Forces Flashcards
(92 cards)
1
Q
What are scalar quantities? (V F Ph)
A
have magnitude (size) only, they don’t have a direction.
2
Q
What is an example of a scalar quantity? (V F Ph)
A
Distance
3
Q
What is a Vector quantity? (V F Ph)
A
Commiting crimes with both direction and magnitude
4
Q
What is an example of a vector quantity? (V F Ph)
A
Displacement (distace in a specific direction)
5
Q
What does the length of the arrow represent? (V F Ph)
A
the magnitude of the vector.
6
Q
What does the direction of the arrow represent? (V F Ph)
A
the direction of the vector
7
Q
What is the definition of a force? (CaNC F Ph)
A
is a push or a pull that acts on an object due to the interaction with another object. All forces have both magnitude and a direction.
8
Q
What type of quanitiy is force? (CaNC F Ph)
A
Vector quantity
9
Q
What is the unit of force? (CaNC F Ph)
A
Newtons (N)
10
Q
What two catagories can forces be put into? (CaNC F Ph)
A
Contact and Non-Contact
11
Q
What do two objects have to be doing to be considered as contact forces? (CaNC F Ph)
A
Physically touching
12
Q
What is are the examples of contact force? (CaNC F Ph)
A
- Tension - (in a rope)
- friction
- air resistance - (air particles)
- normal
13
Q
What do two objects have to be doing to create a non contact force? (CaNC F Ph)
A
the two objects have to be physically seperated
14
Q
What are the examples of non contact forces? (CaNC F Ph)
A
- Gravitational force attracts all objects to other objects (Gravity attracts the International Space Station to Earth and Earth to the International Space Station)
- electrostatic force is the force between to charged objects (opposites attract)
- magnetic force which is the force experienced by certain objects in a magnetic field.
15
Q
What does the mass tell us about the object, and what is the unit? (GaW F Ph)
A
the mass of an object tells us how much matter the object has in it, the unit is in kg
16
Q
What type of quantity is mass? (GaW F Ph)
A
scalar
17
Q
Does mass depend on where the object is? (GaW F Ph)
A
No, a box of 50kg is on earth and is still 50kg on the moon
18
Q
What is the weight of an object due to, and what is it measured in? (GaW F Ph)
A
the force acting on an object due to gravity, measured in Newtons
19
Q
Does the weight of an object depend on where it is? (GaW F Ph)
A
Yes, weight is the mass times the gravitational field strength.
20
Q
What is the equation for figuring out weight and their units? (GaW F Ph)
A
weight (N) = mass (kg) x gravitational field strength (N/kg)
21
Q
What is the proportional relationship conecting mass and weight? (GaW F Ph)
A
weight is directly proportional to mass, if the mass doubles the weight will also double.
22
Q
What does the gravitational field strength depend on? (GaW F Ph)
A
Where you are e.g earth or the moon
23
Q
Where can the weight of an object be considered to act at? (GaW F Ph)
A
A single point, the centre of mass
24
Q
What is the centre of mass? (GaW F Ph)
A
The single point in which the weight of an object can be considered to act as
25
What is a resultant force? (RF F Ph)
a single force that has the same effect as all of the original forces acting together.
26
How do you work out the resultant force when the forces are opposing eachother? (RF F Ph)
subtract the smaller force from the larger force.
27
What does constant velocity and constant altitude mean in terms of forces? (RF F Ph)
The forces pushing and pulling are balanced
28
How do you calculate the resultant force when the forces are at angles to each other? (RF F Ph)
- Draw a vector diagram showing the forces involved. e.g 1cm = 1N
--- Draw a dot to show the object and use a ruler to draw an arrow for the Newtons
--- Use a Protractor to measure the degrees between the two forces, draw another arrow
--- make a parralellogram off of these two lines. Copy the first one and attach it to the second, copy the second one and attach it to the first
--- use a protractor to double check the angle
--- draw from the dot to the opposite end of the parralellogram and measure it.
29
What is work done and the unit? (WDaET F Ph)
energy transfered meausred in J
30
How do you calculate work done and the units? (WDaET F Ph)
Force (N) x distance (m)
31
What does the distance in the equation for work done depend on? (WDaET F Ph)
the distance must be in the line of action to the force
e.g a person going up the stairs has gravitational potential energy acting on them and it is acting downwards so you only count the distance of the stairs going up, not across.
32
What does distance tell us? (S F Ph)
How far an objects moves. Not direction
33
What type of quantity is distance? (SWA CC Ch)
Scalar
34
What does displacement tell us? (SWA CC Ch)
the distance that an objects moves in a straight line from the start point to the finish point. and must include direction
35
What type of quantity is displacement? (SWA CC Ch)
vector as it requires direction e.g east
36
What does speed tell us?(SWA CC Ch)
the speed of an object tells us the distance the object travelled in a given time
37
What type of quantity is speed? (SWA CC Ch)
scalar
38
What is the equation for speed and the units? (SWA CC Ch)
**speed** m/s = **distance** m *divided* by the **time** s
39
What is the normal walking speed? (SWA CC Ch)
1.5 m/s
40
What is running speed? (SWA CC Ch)
3 m/s
41
what is cycling speed? (SWA CC Ch)
6m/s
42
What are some factors that can affect the speed of people (running, walking, cycling) (SWA CC Ch)
the terrain and the age and the distance travelled
43
44
What is the speed of a car on a main road? (SWA CC Ch)
13 m/s
45
What speed it a fast train in the uk? (SWA CC Ch)
50 m/s
46
What is the speed of a cruising aeroplane? (SWA CC Ch)
250 m/s
47
What is the speed of sound in the air? (SWA CC Ch)
330 m/s (but this can vary as it travels faster of warmer days)
48
Is the speed of a moving object often constant? (SWA CC Ch)
No it is rarley constant. so we use the average speed over the whole journey.
49
Are we stating speed or velocity: 20m/s South? (V F Ph)
velocity becuase we talk about the direction and the magnitude
50
Are we stating speed or velocity: 20m/s? (V F Ph)
Speed
51
How do we workout the velocity? (V F Ph)
speed = distance / time
and then say which direction
52
What is the special case for velocity and how do we descirbe it? (V F Ph)
- when an object is moving in a circle
- If an object is moving at a constant speed in a circle then its velocity is constantly changing even though its speed is constant
- this inclued traveling in a part of the circle.
53
What does the acceleration of an object tell us? (A F Ph)
the change in the velocity of an object over a given time.
54
How do we calculate the acceleration, with units? (A F Ph)
acceleration (m/s2) = change in the velocity (m/s) / time (s)
55
What do we call it when an object is slowing down in a period of time? (A F Ph)
deceleration
56
Appart from the equation, how do we calculate the acceleration? (A F Ph)
a velocity time graph
57
Which part of the velocity time graph tells us the acceleration? (A F Ph)
the gradient of the line
58
What does the gradient of the line tell us in a velocity time graph? (A F Ph)
the acceleration
59
Which part of a velocity time graph tells us the displacement? (A F Ph)
the area underneath the line
60
What does the area underneath the line in a velocity time graph tell us? (A F Ph)
the displacement
61
How do you calculate the displacement of a velocity time graph if the acceleration/ decceleration is not constant? (not straight) (A F Ph)
we need to count the squares.
Count how many complete / almost complete squares and then estimate the total of the parts of the squares.
Then times this number by the area of just one square to get the right size
62
What is the equation for when an object is accelerating at a constant rate and units? (A F Ph)
final velocity2 - inital velocity2 = 2 x accelertaion x distance
v2 (m/s) - u2 (m/s) = 2 x a (m/s2) x s (m)
63
Around What value is the initial acceleration when any object falls towards the surface of earth? (A F Ph)
And why?
9.8 m/s2
due to the force of gravity acting on the object
64
What does terminal velocity mean? (A F Ph)
When an object is falling, after some time, the force of the air resistance balances the force due to gravity. At this point the object stops accelertating and moves at a constant velocity. This applies to when an objec is falling through a fluid e.g air or liquid.
65
How do you work out the speed for a distance time graph? (DTG F Ph)
the gradient
66
What is the stopping distance? (VSD F Ph)
the total distance travelled from when the driver first spots the obstruction to when the car stops.
67
What are the two parts of stopping distance? (VSD F Ph)
- thinking distance
- braking distance
68
What is the thinking distance? (VSD F Ph)
the distance travelled by the car during the driver's reaction time.
69
What is the reaction time? (VSD F Ph)
the time taken for the driver to spot the obstruction, make a desicion and then move their foot onto the brake.
70
What is the breaking distance? (VSD F Ph)
the distance the car travels from when the driver applies the brakes to when that car stops.
71
What is the correlation between the speed of a car and the stopping distance? (VSD F Ph)
the faster the car is going, the longer the stopping distance will be.
72
What is the range of a typical person's reaction time? (VSD F Ph)
0.2 s and 0.9 s
73
What is the stopping distance for a car travelling at 30mph?
23m
74
What are things that can affect a reaction time? (VSD F Ph)
- tierdness
- alcohol and certain drugs
- distractions in the car e.g mobile phone
75
What can affect the braking distance? (VSD F Ph)
- wet or icy roads can reduce the friction between the tyres and the road and increase the braking distance
- worn down tyres as it also reduces the friction
- worn brakes
76
How do you calculate kinetic energy? and units (FB F Ph)
kinetic energy (J) = 1/2 x mass (kg) x velocity squared (m/s)
77
What happens to the kinetic energy of the car when it brakes? (FB F Ph)
converted to thermal energy in the brakes. which causes the temperatures of the brake to increase. At the same time, the car slows down as it loses kinetic energy.
78
What is the correlation between the speed of a car and the breaking force needed to stop the car in a certain distance? (FB F Ph)
the faster the car is going, the greater the stopping force required.
79
What are the dangers when a car is going fast and the braking force is high meaning a large amount of kinetic energy transfered to thermal energy in the breaks? (FB F Ph)
- the brakes can overheat
- the driver can lose control of the vehicle
80
What is the set up for the practical for acceleration? (RP7A F Ph)
- A toy car which is attached to a piece of string.
- This string is looped around a pulley.
- The other end of the string is attached to a 100g mass. This mass will provide the force acting on the toy car.
- We also need a timer
- On the desk we draw chalk lines at equal intervals e.g every 10cm
81
What is the method for the practical of acceleration? (RP7A F Ph)
1. Hold the toy car at the starting point and then let go of it
*becuase of the resultant force acting from the string, the car will accelerate along the bench*
2. record the time that the car passes each distance marker
*if the car is moving rapidly then it will be difficult to record an accurate time.*
***To fix this we can record the experiment and then watch it back and record the times accuratley***
3. Repeat the experiment several times but we decrease the mass on the end of the string
*the weight/ the force decreases each time*
4. Each time we decrease the weight we must add it onto the toy car.
*so that we keep the overall mass of the object the same*
82
What is the relationship between the acceleration of the toy car and the mass on the other end of the string when doing the acceleration practical? (RP7A F Ph)
the acceleration of the toy car is proportional to the mass on the other end of the string
83
How do we investigate how varying the mass of the object using the setup for the experiment for acceleration?(RP7A F Ph)
keep the weight on the string constant but we add a mass onto the toy car. Record the car as it accelerates across the bench. Then we repeat the experiment by increasing the mass attached to the toy car.
When we increase the mass of the toy car, the acceleration decreases.
84
(VSD F Ph)
85
1. What is the only force acting on a skydiver when they jump out of the plane? (FOS F Ph)
weight which is due to gravity and this force does not change during the journey. Because of this the skydiver experiences a resultant force acting downwards so they accelerate towards the ground
86
2. What is the second thing the skydiver will experience as they fall? (FOS F Ph)
friction with the air molecules / air resistance and it acts upwards. However the weight it still greater than the air resistance so the skydiver continues to accelerate towards the ground. As the velocity increases, the air resistance also increases. The air resistance will balance the weight. So there is no resultant for and the velocity stays constant. aka terminal velocity. This velocity is great and if they hit the ground they would die.
87
3. At what point should a skidiver open their parachute and describe what happens as a result of this? (FOS F Ph)
When they reach terminal velocity. The surface area now increases and this causes the air resistance to massivley increase. At this point the air resistance is now greater than the weight so there is a resultant force acting upwards. This causes the skydiver to decelerate. Because the velocity has decreased, the air resistance also decreases. At some point the air resistance with balance the weight and the resultant force will be 0 and at this point the velocity will stay constant. They are now travelling at a low terminal velocity and it is safe for them to hit the ground.
88
Describe in terms of forces, a skydivers journey from jumpping to landing.
as soon as the skydiver jumps out of the plane, the only force is weight. The sky dive accelerates towards the ground. As the skydiver falls, air resistance acts upwards. Weight is still greater than air resistance, so the skydiver continues to accelerate. Also, velocity increases. Air resistance also increases.
When air resistance balances weight, the resultant force is 0 and the velocity stays constant. This is the terminal velocity. At this point, the skydiver opens up the parachute.
The surface area now increases on the air resistance and massively increases. The air resistance is now greater than the weight, so the resulting force now acts upwards. Because there was ultimate forces now acting upwards, the skydiver now decelerates. They're still moving towards the ground, but at a much lower velocity.
Because the velocity has decreased, the air resistance also decreases. When air resistance balances the weight, the resultant force is 0. The velocity is now constant and this is a lower terminal velocity. Finally, the skydiver lands.
89
What is the unit for pressure? (PF F Ph)
pascal (Pa)
90
What is the units for area of the surface when calculating the pressure? (PF F Ph)
metres squares (m2)
91
Where in the atmousphere is it most dense? (PF F Ph)
closest to the earths surface.
at the earths surface, there are the greatest number of air molecules in a given volume
92
