Topic 5 Flashcards
(163 cards)
1
Q
What is a scalar quantity?
A
It is a quantity that only has a magnitude(size) not a direction.
2
Q
Name 6 scalar quantities?
A
Mass, Temperature, Speed, Energy, Distance and Time
3
Q
What is a vector quantity?
A
A vector quantity has both a magnitude and a direction.
4
Q
Name 6 vector quantities?
A
Displacement, Weight, Force, Velocity, Acceleration and Momentum.
5
Q
What is Displacement?
A
It is Distance in a specific direction.
6
Q
Why is Distance a scalar quantity?
A
It gives us no idea of the Direction
7
Q
How do you represent vectors?
A
With arrows.
8
Q
The length of the arrow tells you what?
A
It represents the magnitude of the vector.
9
Q
What does the direction of the arrow represent?
A
The direction of the vector.
10
Q
What is a Force?
A
It is a push or a pull that acts on an object due to the interaction with another object.
11
Q
What can forces be?
A
Contact or Non contact forces.
12
Q
What are contact forces?
A
The two objects are physically touching.
13
Q
Name 4 contact forces?
A
Tension, Friction, Air resistance and Normal contact force.
14
Q
What is Friction?
A
A force that is created when two surfaces move or try to move across each other.
15
Q
What happens when Friction acts between water and an aeroplane?
A
It causes the aeroplane to slow down and come to a stop.
16
Q
How is Air-resistance shown with a skydiver?
A
As the skydiver falls through the air, the air particles collide with the parachute, this causes the force of air resistance to act upwards.
17
Q
How does a lamp on a table use a normal contact force?
A
The lamp exerts a force downwards on the table which is the weight of the lamp, at the same time the table is exerting an upwards force on the lamp, which is called a Normal contact force, which can only happen if two objects are in direct contact.
18
Q
What is a Non-contact force?
A
The two objects are physically separated, but the force can still act.
19
Q
Name 3 non contact forces?
A
Magnetic force, gravitational force and electrostatic force.
20
Q
What does a Gravational force do?
A
It attracts all object to other objects
21
Q
What does the Gravitational force do to the International space station to the earth?
A
It attracts the International space station to the earth and the Earth to the International space station.
22
Q
What is a Electrostatic force?
A
It is the force between two charged particles.
23
Q
Objects with Opposite charges experience what?
A
An electrostatic force of attraction
24
Q
Objects with the same type of charge experience what?
A
An electrostatic force of repulsion.
25
What is a Magnetic force?
It is the force experienced by a certain object in magnetic field.
26
What is mass?
A mass of an object tells us how much matter their is in an object
27
The mass doesn't depend on what?
Where the object is e.g an elephant with a mass of 5000 kg on earth has the same mass on the moon.
28
What is the weight of an object?
Is the force acting on it due to gravity.
29
The does the weight of an object depend on?
It depends on where the object is e.g An object with a mass of 1 kg, if it placed on the surface on the earth, then it experiences a gravitational force towards center of earth, the center of earth is 9.8 N/kg so the weight would be 9.8 N but on the moon it would be different.
30
What is Gravitational force?
It is a measure of the force of gravity in a particular location which depends where you are.
31
How can you measure weight of an Object?
Weight(N)=Mass(kg) X Gravitational field strength(N/Kg)
32
The weight is what to the mass?
The weight is directly proportional to the mass.
33
What is the center of mass?
The weight acting on an object which can be considered to act at a single point.
34
Traffic cones how a Wide base which means what?
They have a low center of mass making it less likely that the cone will topple.
35
How do you find center of mass on an irregular object?
1) Make a hole on the top of the object or were ever you like
2) Put a pin in the hole so it stands up freely
3) Attach piece of string with weight on the pin
4) Draw a vertical line were the string rests on an object
5) make a second whole on the object in another position and repeat process
6) Where the two lines cross shows the centro of mass
36
What is a Resultant force?
It is an overall force on a point or object
37
A man applies a force on a block of 20 N to the right, A friction force of 10 N is acting on the left what is the resultant force?
Resultant force = 20 N - 10 N = 10 N to the right.
38
How do you calculate resultant forces?
To work out resultant forces you subtract the smaller force from larger force.
39
A car on a road has a driving force of 10000 N acting to the left, it has Air resistance acting to the right and finally a friction force with the road of 400 N acting to the right what is the Resultant force?
The resultant force is:
Find resultant force acting on the right so 5000+4000n=9000n to the right
Subtract 9000N from the driving force
This gives us a resultant force of 1000N.
40
A skydiver is falling down from the air at a constant velocity, the Skydiver's weight experiences a force of weight 800 N acting downwards and also experiences an upwards force of 800 N of air resistance what is Resultant force?
800 N - 800 N = 0N the resultant force is balanced and Zero
41
What does a free body diagram show?
All the forces acting on a object.
42
How do you draw a free body diagram?
1) The object is shown as a point
2) The forces are drawn as arrows starting at a point
3) The length of arrow shows us the size of force and direction of arrow shows the Direction of force.
43
When a force causes an object to move through a distance what happens?
Work has been done causing object to move
44
When is Work not done?
When the Object doesn't move in the direction of force.
45
How do you calculate work done?
W(N) = Force (N) X Distance (traveled by object, M)
46
What is the Unit of work?
One joule of work is done when a force of one newton causes an object to move a distance of one meter.
47
How do you convert joules into newton meters?
1 J = 1 N/m
48
You can use a scale diagram to find what?
The resultant force
49
What are the 3 rules of scale diagrams to find resultant force?
1)Draw all forces acting on object to scale tip to til
2 Draw a straight line from the start of the force to the end of the last force to find resultant force
3)Measure length of Resultant force on the diagram to find magnitude and the angle to find direction of the force.
50
Name 3 examples of Elastic materials?
Slinky, rubber bands and gloves
51
What is an Elastic material?
It will always return to their original length or shape if we take away the forces acting on them.
52
What happens when a force is applied to Elastic material?
The forces are equal in magnitude but opposite in direction causing the forces to stretch.
53
When we apply a squeezing force to an elastic material what happens?
This causes materials to compress, but if we take away the forces, it returns to its original length
54
If we apply more than 2 forces to an elastic material what does it cause it to do?
This causes the elastic material to bend but if we remove forces then it returns to its original length.
55
What is Elastic deformation?
when the elastic material can go back into its original shape and length after the force has been removed.
56
What is Inelastic deformation?
When the inelastic material do not return to their original length when force is removed.
57
In order to change an objects length or shape what do you have to do?
you have to apply more than one force.
58
What happens if you apply one force to a stationary object?
The forces are no longer balanced meaning the object would move rather than changing shape or length.
59
What is the equation of finding the force needed to stretch an elastic object?
F(force)= k(spring constant(N/m) X Extension(m)
60
Calculate the force required to extend a spring by 0.04 meters, the spring constant is 200 n/m?
F = K X E
200 N/m X 0.04 m=
F=8 N
61
Do we have to use another equation to calculate the compression when an elastic object is squeezed?
No we just have to change extension to Compression
62
When we stretch or compress an elastic object what ae we using?
We are using a force to do work,.
63
What is stored in an elastic object when using a force to do work?
Elastic potential energy is stored
64
What is work done equal to?
It is equal to the elastic potential energy, this only true if object is not in elastically deformed
65
What is the required practical involving a spring and a meter ruler?
Investigating the relationship between the force applied to a spring and its extension.
66
What is the method of Investigating the relationship between the force applied to a spring and its extension.
1) Get a ruler and clamp it to a stand
2) Add the spring then measure it first with a ruler which no force applied
3) Add mass to the spring and allow it to come to rest, record the mass and measure length of spring, the extension is the change in length
4) Repeat the process until you have enough measures.
67
What is the Gradient on the graph plotted when the results of the investigation, Investigating the relationship between the force applied to a spring and its extension is drawn?
The gradient is equal to the spring constant.
68
What is Elastic potential energy?
is the energy stored when a force is applied to an elastic object causing it to stretch or compress.
69
What is the extension directly proportional to?
The force applied.
70
What is Limit of proportionality?
When the line begins to bend the spring has been stretched beyond limit of proportionality meaning it cannot return back to its original length if we take the force away.
71
What is doing work?
Applying a force.
72
What is the formula to calculate the energy stored in a springs elastic potential energy store?
Ee (Elastic potential energy (J))= 0.5 X K(spring constant(N/m) x e2(extension(m)
73
What is distance?
it is how far an object has moved (scalar)
74
What is Displacement?
It tells you the distance that an object moves in a straight line from the start point to the finish point, which must include direction of a straight line (Vector)
75
If you walk 5 m north, then 5 m south what is your displacement and direction?
Displacement is 0m
| Distance is 10 m
76
What is speed?
How fast an object travelling (scalar)
77
What is Velocity?
How fast an object moves in a given direction (Velocity)
78
What does the speed of an object tell you?
The distance the object has traveled in a given time
79
What is the Equation for speed?
Speed(m/s symbol V) = Distance(m symbol s)/ time(s symbol t)
80
What is the normal walking speed?
1.5m/s
81
What is the running speed?
3m/s
82
What is cycling speed?
6m/s
83
What is the speed of a car?
25m/s
84
What is speed of a train?
30m/s
85
What is the speed of a plane?
250m/s
86
Why is speed average speed?
because objects rarely travel at a constant speed
87
A person walks in a straight line from point a to point b, covering a distance of 50 m. this takes 40 s. Calculate the person's velocity?
Speed(m/s) = 50m/40s
| = 1.25 m/s south
88
If an object moves at a constant speed what happens?
Then the velocity is constantly changing even through its constant speed.
89
What is acceleration?
is how quickly your speeding up
90
What does the acceleration tell you?
the change in the velocity over a given time.
91
What is the equation for velocity?
acceleration (m/s2 symbol a)= change in velocity symbol(delta v)/ time(s) (symbol t)
92
A cyclist is travelling at a velocity 6 m/s east. Here the velocity reduces to zero in 12 seconds. Calculate the acceleration of the object?
0-6/12 = -0.5m/s squared
93
If the acceleration is negative what is the object doing?
Decelerating.
94
If an object is accelerating at a constant rate then what equation do you use?
v squared (Final velocity(m/s) - u squared(initial velocity(m/s) = 2 X a(acceleration (m/s squared) x s(distance m)
95
What is constant acceleration known as?
Uniform acceleration
96
When any object falls towards the ground what is it's initial acceleration?
9.8 m/s squared
97
Why is the intial acceleration of an object when it falls on the ground 9.8 m/s squared?
This is due to the force of gravity acting on the object
98
Describe the motion of a skydiver falling down?
1) As skydiver falls, he experiences an upward force of friction with the air particles called air resistance
2) After some time the force of the air resistance balances the force due to gravity
3) At this point, the object stops accelerating and moves at constant velocity
99
What does the gradient of a distance- time graph show?
Speed
100
What does a curve represent in a distance- time graph?
Accelerating or decelerating
101
How do we determine the speed of an object at any given point?
Find gradient of a tangent.
102
In a velocity time graph what does the gradient show?
The acceleration
103
On a velocity time graph what does a horizontal line show?
Constant velocity
104
What does a curve mean in a velocity time graph?
Changing acceleration or deceleration
105
The steeper the line of a velocity time graph?
The greater the acceleration or deceleration
106
What does the area under any section or all of the graph show?
The distance traveled in their time interval
107
If the section under the graph is irregular how do you find the area?
Count the squares
108
Describe what is meant by Terminal velocity on a falling object or fluid?
When an object is dropped downwards from a large height, before it starts to move downwards, the only force acting on it will be it's weight.
2) It will accelerate downwards due to gravity at the surface of the earth 9.8 m/s squared
3) As the object moves downwards it will begin to push air particles out of its way and the air resistance acting on it which is 0 increases.
4) As velocity increases it has to push more and more air particles out of its way every second meaning air resistance gets larger and larger
5) At the point the object at which the air resistance has increased to the point at which it is equal to the weight
6) When this happens the resultant force is 0 and no longer accelerate, which means that it has reached terminal velocity.
109
In water the force pulling an object upwards is what?
Drag
110
What does less streamlined object have lower of?
It has a lower terminal velocity
111
Do objects with a large surface area have low or high terminal velocities?
Lower terminal velocity
112
If you dropped a marble and a beach ball of a tall building which would have a higher terminal velocity?
The marble would have a higher terminal velocity because there is more air resistance acting on the beach ball, at any given speed, so this means that the beach ball spends less time accelerating before the air resistance is large enough to equal the accelerating force.
113
What is Newtons first law?
If a stationary object experiences a resultant force to zero, then it will remain stationary. If a moving object experiences a resultant force of zero, it will continue moving at the same speed and in same direction
114
For example if a object experiences 2 equal forces acting on both sides what happens to the object?
The resultant force is zero therefore the object remains stationary
115
Another example if a car is at constant speed of 15 m/s what happens to car?
Because it is at constant speed it will experience the same force action in the opposite direction called resistive forces meaning the car will carry on moving at same speed.
116
If the resultant force is non zero what happens to the object?
It will produce a acceleration or deceleration in the direction of the force
117
What is Newtons 2nd law?
The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of an object.
118
What does newtons 2nd law actually mean?
The greater the force, then we have a greater acceleration. Also if mass is larger then the acceleration will be smaller
119
Which will experience a greater acceleration a object with a mass of 1 kg and a resultant force of 20 N to right or another object with a mass of 2 kg and a resultant force of 20 N to the right?
The top object will experience more of a force meaning greater acceleration.
120
What is the equation to find the force needed to accelerate an object?
Force(N) = Mass kg X Acceleration (m/s squared)
121
A van of a mass of 2080 kg has an engine that provides a driving force of 5200 N. At 70 mph the drag force acting on the van is 5148 N. Find its acceleration at 70 mph?
Work out resultant force of van = 5100 - 5148= 52 N
rearrange equation = a = f/m
52 N / 2080 = 0.025 m/s
122
What does Inertia mean ?
Object will stay still or keep the same motion unless you apply a resultant force.
123
What is the inertial mass?
The inertial mass is a measure of how difficult it is to change the velocity of an object
124
How can you calculate the inertial mass?
Using Newtons 2nd law equation, and rearrange it to find mass, so the inertial mass is just the ratio of force over acceleration
125
What is Newtons third law?
Whenever two objects interact, the forces they exert on each other are equal and opposite.
126
Explain the forces when a man is on a canoe?
The man uses the paddle to push on water, at the same time the water pushes back on the paddle, this forces is equal in magnitude but opposite in direction.
127
Explain what happens when a skater which has a mass of 55 kg exerts a force on skater B which has a mass of 65 kg?
When skater A pushes on skater B she feels an equal and opposite force from skater b's hands (normal contact force), both skaters feel the same sized force but in opposite directions, and so accelerate away from each other. Skater A will accelerate more than skater B, because she has a smaller mass (A=f/m)
128
Explain newtons third law in an equilibrium situation with a man pushing against a wall?
As the man pushes on the wall, there is a normal contact force acting back on him, these two forces are the same size. As the man applies a force and pushes the wall, the wall 'pushes back' on him with an equal force.
129
Explain why you don't move when you lean on a wall, even though you are exerting a force?
When you lean on a wall, you exert a force on the wall. Due to Newtons third law, the wall also exerts an opposite force which is a normal contact force back on to you. You also exert a force on the ground and the ground exerts a force on you. The resultant force is zero so you remain stationary.
130
What is the experiment that links to newtons second law?
Investigating how the resultant force and mass effects an objects acceleration.
131
What is the independent variable when investigation how the resultant force affects the acceleration of a object?
The resultant force
132
What is the dependent variable when investigation how the resultant force affects the acceleration of a object?
Acceleration
133
What is the control variable when investigation how the resultant force affects the acceleration of a object?
Mass
134
What is the independent variable when investigation how the mass affects the acceleration of a object?
Mass
135
What is the dependent variable when investigation how the mass affects the acceleration of a object?
Acceleration
136
What is the Control variable when investigation how the mass affects the acceleration of a object?
Resultant force
137
What is the method of investigating how the resultant force affects the acceleration of an object?
1) Set up apparatus including a piece of card on a trolley, pulley, hook of known masses, masses light gate and data logger
2) Connect trolley to a piece of string that goes over a pulley and it is connected on to a hook on the other side.
3) The accelerating force will be the mass of the hook X acceleration due to gravity which is 9.8 m/s
4) Mark a start line on table so that trolley always travels same distance to light gate
5) add masses to the masses and holding hook of string release it.
6) Record acceleration measured by light gate and data logger
7) to find mass rearrange newtons second law to find mass.
138
What is the method of investigating how the mass affects the acceleration of an object?
1) change masses attached to the hook but put masses on the trolley
2) you find out as mass increases the acceleration of trolley decreases
3) acceleration is inversely proportional to interital mass
139
What is stopping distance?
It is the total distance over which a car comes to rest
140
What is the thinking distance?
It is the distance traveled while reacting
141
What is the braking distance?
It is the distance traveled between a point at which brakes are applied and point at which a car comes to rest.
142
What is the equation for stopping distance?
Thinking distance + Braking distance
143
What is the thinking distance directly proportional to?
to the speed of the car
144
What is the braking distance directly proportional to?
it is proportional to the speed of the car squared.
145
What is the 3 typical car breaking distances?
14 m at 30 mph, 55 m at 60 mph and 75 m at 70 mph.
146
What two things affect your thinking distance?
Your speed - the faster you're going the further you will travel during the time you will react
Reaction time- the longer reaction time, the longer your thinking distance
147
What things affect your braking distance?
Wet icy conditions - they reduce friction between tyres and the road causing vehicle to skid.
Worn tires - reduces friction between tyres and road.
Speed- the faster the vehicle travels, the longer it takes to stop.
148
What does driving slowly mean?
reduces the breaking force needed to stop in a given distance.
149
Describe what happens during braking?
The brake presses against the wheel, the force of friction now acts between the brake and the wheel. The kinetic energy of the car is now converted into thermal energy in the brakes causing the temperature to increase.
150
What causes brake's to heat and driver to lose control over the vehicle?
Applying a large amount of kinetic energy which is transferred into thermal energy in the brakes.
151
What does the kinetic energy depend on?
The velocity squared.
152
A car with a mass of 1000 kg is travelling at 30 m/s on the motorway. they decelerate to leave the motorway their velocity decelerates to zero in ten seconds. Estimate the force involved in decelerating of the vehicle in public road.
```
F=ma
m = 1000 kg
a=change in velocity/ time
=30-0/10= 3 m/s
f= ma
f = 1000kg X 3 m/s squared
=3000N
```
153
All moving objects have what?
Momentum
154
If objects is not moving does it have momentum or not?
It has no momentum
155
What is the equation of momentum?
Momentum (kg m/s P) = Mass(kg) X velocity(m/s)
156
What is the conversation of momentum?
In a closed system, the total momentum before an event equals total momentum after an event.
157
Describe how momentum is conserved(remains the same) by a gun recoiling(moving backwards) as it shoots a bullet?
1) Before the cannon fires, both the cannon and the cannon ball are not moving so the momentum equals zero.
2) When cannon fires, the cannon ball is moving at a large velocity, so the cannon ball has a forward momentum.
3) At the same time the cannon has momentum acting in the backwards direction.
4) This backwards momentum is equal to the forwards momentum of the cannon ball
5) Therefore the total momentum is zero, the momentum before was zero and the momentum after firing is zero
158
Describe how momentum is conserved by a van hitting a stationary car?
The van is moving towards a stationary car, which means the van has a forward momentum.
2) the stationary car has no momentum as it is moving, when the van collides with car, both the van and car move together
3) the velocity is slower than the initial velocity
4) The total momentum of the van and the car together , it now the same as the initial momentum of the van by itself.
5) the total momentum before a collision is the same as the total momentum after the collision meaning momentum has been conserved.
159
Is momentum a scalar or a vector?
Vector
160
The energy in the elastic potential energy store of a streched spring is equal to what?
The area under the force-extension graph to the limit of proportionality.
161
Why do objects with a large surface area have lower terminal velocity?
Less streamlined an object is the lower its terminal velocity.
162
Eric the Astronaut is stranded in deep space, where the local gravitational field strength if 0 N/kg.State Newton’s first law, and explain what it can tell us about the motion
of Eric in deep space
If there is no resultant (net) force acting on an object then it will not accelerate it will remain at constant velocity This means that Eric’s velocity will be constant.
163
How do you find out reaction time when ruler is caught at 20 cm?
Use the equation v2-u2=2as
rearrange to find V
u=0 a = 9.8 m/s2 and s= 0.2m so v =square root 2 X 9.8 X 0.2 + 0 =1.97....m/s
v= change in velocity of the ruler
you also know: a = change in velcoity /time so t = change in velocity / a = 1.97... / 9.8 = 0.202...
s = 0.2s
