P10 - Force and Motion Flashcards
1
Q
What is braking distance?
A
the distance travelled by a vehicle during the time it takes for its brakes to act
2
Q
What is conservation of momentum?
A
in a closed system, the total momentum before an event is equal to the total momentum after the event.
Momentum is conserved in any collision or explosion, provided no external forces act on the objects that collide or explode
3
Q
What is directly proportional?
A
a graph will show this if the line of best fit is a straight line through the origin
4
Q
What is an elastic material?
A
a material is elastic if it is able to regain its shape after it has been squashed or stretched
5
Q
What is extension?
A
the increase in length of a spring (or a strip of material) from its original length
6
Q
What is gravitational field strength, g?
A
the force of gravity on an object of mass 1 kg (in newtons per kilogram, N/kg). It is also the acceleration of free fall
7
Q
What is inertia?
A
the tendency of an object to stay at rest or to continue in uniform motion
8
Q
What is limit of proportionality?
A
the limit for Hooke’s law applied to the extension of a stretched spring
9
Q
What is mass?
A
the quantity of matter in an object / a measure of the difficulty of changing the motion of an object (in kilograms, kg)
10
Q
What is the equation for momentum?
A
mass (in kg) x velocity (in m/s)
11
Q
What is Newton’s second law of motion?
A
the acceleration of an object is proportional to the resultant force on the object, and inversely proportional to the mass of the object
12
Q
What is stopping distance?
A
the distance travelled by the vehicle in the time it takes for the driver to think and brake
13
Q
What is terminal velocity?
A
the velocity reached by an object when the drag force on it is equal and opposite to the force making it move
14
Q
What is thinking distance?
A
the distance travelled by the vehicle in the time it takes the driver to react
15
Q
What is weight?
A
the force of gravity on an object (in newtons, N)
16
Q
What is acceleration?
A
the rate at which an object changes its velocity. It is measured in m/s²
17
Q
What is a force?
A
A push or a pull that acts upon an object
18
Q
What is inertial mass?
A
A measure of difficulty in changing an objects velocity
19
Q
What is terminal velocity?
A
The maximum velocity of a free falling object, when the air resistance is equal to its weight
20
Q
What is the stopping distance?
A
thinking distance + braking distance
21
Q
What is the breaking distance?
A
The distance taken to stop once the breaks are applied
22
Q
What is the thinking distance?
A
The distance travelled in between the driver realising he needs to break and actually breaking
23
Q
What is momentum?
A
Mass x Velocity
24
Q
What is the gravitational field strength on earth?
A
9.81 m/s²
25
What is newtons first law of motion?
An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an external force
26
What is newtons second law of motion?
Force = Mass x Acceleration
27
What is newtons third law of motion?
For every action there is an equal and opposite reaction
28
Which of newtons laws refer to inertia?
Newtons first law of motion
29
What quantity determines the magnitude of a body's inertia?
mass
30
What are the conditions needed for a body to be stationary?
The resultant force on the object must be 0 and it must already be stationary
31
What are the conditions needed for a body to be moving at a constant speed?
The resultant force on the object must be 0 and it already be in motion
32
What are the conditions needed for a body to be moving at a constant acceleration?
The resultant force on the object must be in the direction it is travelling and it must already be in motion.
33
What is the resultant force on an object?
The net force acting upon an object. The resultant force has the same effect as all the forces acting upon an object combined
34
Why did people believe that F = mv and not F = ma before newton formulated his 3 laws of motion?
People believed that a force was needed in order to keep a body moving at a constant speed, however newton showed us that forces are balanced on an object moving at a constant speed and that a resultant force will make a body accelerate
35
What is the equation for acceleration according to newtons second law of motion?
a = f/m
36
If a force of 2000N is applied to a car with a mass of 1000kg at what rate will it accelerate at?
2 m/s²
37
If the force of an engine is applying a force of 1000N forward on a car with a mass of 1000kg but drag and friction from the wheels apply 600N in the opposite direction, at what rate will the car accelerate?
400/1000 = 0.4 m/s²
38
If a lorry weighs 8000kg, what force is needed to accelerate it at 0.6m/s²?
0.6 x 8000 = 4800N
39
Describe the method on the practical for investigating force and acceleration
1) Measure the length of each card segment
2) set up the apparatus as follows: the card segments on the trolley, the piece of string attached to the trolley hanging over the edge of the desk on the pulley, the masses holder attached to the other end of the string, and the light gate positioned at the same height as the card segments
3) Attach the data logger to the the light gate and set it up as required
4) Add masses to the mass holder so that the total mass, including the holder, is 250g
5) Pull back the trolley, set the data logger to record, and then let the trolley run to the pulley. Collect the necessary measurements from the data logger
6) Take 50g off the mass holder and place it onto the trolley. Repeat step 5
7) Repeat steps 5-6 until only 50g is left
8) Record the acceleration of each mass 2-3 times to get more accurate results and it allows you to get a mean average on the results.
9) Record these results in an appropriate table and graph
40
Describe the relationship with the acceleration of an object and the force applied to the object
as the force applied increases, the acceleration increases
41
State a possible source of error in the practical for investigating force and acceleration
there was friction which could change the acceleration of the trolley
42
Why were masses taken from the holder then placed on the trolley in practical for investigating force and acceleration
To keep the mass in the system the same
43
If the resultant force on an object is doubled, what will happen to the acceleration?
it will double
44
If the mass an object is doubled, what will happen to the acceleration?
It will half
45
How does a seatbelt reduce the risk of major injury?
A seatbelt stops its user continuing forward (due to inertia) if the car suddenly stops. If someone wasn't wearing a seatbelt they would continue moving forwards and hit the windscreen, this is a "short sharp impact", this increases the impact force and would cause major injury. The time taken for the person to stop is lengthened whilst wearing a seatbelt, this reduces the decelerating force. Furthermore, the seatbelt acts across the chest, so it spreads the force out
46
How does a crumple zone reduce the risk of major injury?
Crumple zones increase the impact time to lessen the impact force
47
How does an airbag reduce the risk of major injury?
Airbags in a car are designed to protect the driver and front passenger. The inflated air bag spreads the force of the impact across the persons body, it also increases the impact time. Both of these reduce the impact force
48
Describe the method on the practical for stretching
1) Attach the spring to the clamp stand by hanging it off a clamp, and allow the other end to hang freely over the side of the bench
2) Use the G clamp to fasten the clamp stand to the bench
3) Use the 2 other clamps to hold the ruler vertically, close to but not touching the spring.
4) Measure the length of the spring with no force acting upon it
5) Hang the mass holder from the spring. Check the mass of the holder, and measure the new length of the spring. Record the length of the spring and the mass suspended from it
6) Add 50g (0.5N) mass and measure the length of the spring
7) Repeat step 6 until a total of 250g (including the mass holder) is hanging from the spring. Each time, record the length of the spring and the total mass suspended from the spring
8) Remove a 50g mass
9) Measure the length of the spring
10) Repeat step 8 and 9 until there is no mass hanging from the spring
11) Record all results in an appropriate table with a column for extension when "adding masses", "when removing masses" and "mean"
49
What is the equation for inertial mass?
inertial mass = force/acceleration
50
What is mass measured in?
kg
51
What is weight measured in?
Newtons (N)
52
What is the resultant force on an object at its terminal velocity?
0N
53
What is weight?
The force acting upon an object due to gravity
54
What is the equation for weight?
Weight = Mass x gravitational field strength
55
What factors influence terminal velocity?
Surface Area (Shape), Mass, Gravitational Field Strength
56
How does Surface Area affect terminal velocity?
If an object has a larger surface area, it will experience more air resistance and therefore there will be a greater upwards force. This will reduce the terminal velocity of the object
57
How does mass affect terminal velocity?
An object with a greater mass will accelerate downwards at the same rate as an object the same shape but a smaller mass. However, it will have a larger terminal velocity as although they are accelerating downwards at the same rate there is a larger downwards force on the more massive object as it has a greater weight
58
How does Gravitational Field Strength affect terminal velocity?
If the gravitational field strength is stronger, the object will have a greater weight. This increases the downward force as it is falling and therefore increases the terminal velocity
59
What does the braking force of a vehicle depend on?
The speed of the vehicle, The mass of the vehicle
60
What factors affect stopping distances?
Tiredness alcohol and drugs, The speed of the vehicle, Adverse road conditions, Poorly maintained vehicles
61
How does Tiredness, alcohol and drugs affect stopping distances?
These affect the way the brain works and lengthen the reaction time. Distractions such as mobile phones also lengthen the reaction time. This increases thinking distance so therefore increases stopping distance
62
How does The speed of the vehicle affect stopping distances?
The faster a vehicle is travelling, the further it travels before it stops. This is because both thinking distance and breaking distance increase with increased speed
63
How do Adverse road conditions affect stopping distances?
In wet or icy road conditions breaking distance is increased, this increases stopping distances
64
How do Poorly maintained vehicles affect stopping distances?
Poorly maintained vehicles, such as worn tires or brakes, have a longer breaking distance as their brake and tires are less effective. This increases the stopping distance
65
What is the equation for thinking distance?
Thinking distance = speed of vehicle x reaction time
66
How do you calculate breaking force?
F = ma
67
What is the law of conservation of momentum
In a closed system, the total momentum before and event is equal to the total momentum after the event
68
What is the equation for the deceleration of a vehicle?
v²-u²/2s
69
What is the equation for conservation of momentum?
M1U1 + M2U2 = M1V1 + M2V2
70
What is the equation for acceleration?
Change in velocity/time
71
What is the equation for impact force?
F = (Mass x ΔVelocity) / Time
72
Why are playgrounds fitted with safety cushioning?
It extends the impact time if someone falls. This reduces the impact force as the change in momentum over time is reduced
73
An object is said to be elastic if ..........
It returns to its original shape when the forces deforming it are removed
74
What is Hookes law?
The extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded
75
What is Hookes law as an equation?
Force applied (F) = Spring Constant (K) x extension (m)
76
What is the spring constant?
Spring constant is a measure of the stiffness of a spring up to its limit of proportionality. The higher the spring constant, the stiffer the spring. The spring constant is different for different elastic objects. It is measured in N/m
77
What is an elastic deformation?
elastic deformation is reversed when the force is removed.
78
What is inelastic deformation?
Inelastic deformation is not fully reversed when the force is removed - there is a permanent change in shape.
79
What is the unit of inertial mass?
kg
80
What is a random error?
errors made by the person carrying out the measuring
81
How can random error be avoided?
Repeat the investigation to find a mean average of the result. You must exclude all anomalies
82
Explain the effect that the time of contact between a golf club and golf ball has on the distance that the golf ball travels.
By increasing the time of contact between the golf ball and golf club, the change of momentum of the golf ball is increased. Momentum is given by the equation "momentum = mass x velocity", since the mass of the golf ball is constant, this means the velocity of the golf ball must increase. Increasing the velocity of the golf ball causes it to travel further before coming to rest, increasing the distance the golf ball travel
83
Explain why people going down a slide all have approximately the same speed at the bottom:
When the people are at the top of the slide, they will have a lot of gravitational potential energy. This is given by the equation "mass x height x gravitational field strength". As they travel down the slide, the decreasing gravitational potential energy will be equal to the increase in kinetic energy, this is because of the law of conservation of energy. Kinetic energy is given by the equation "0.5 x mass x velocity²". Although the different riders may have different masses, this cancels out of the equations, so "0.5 x mass x velocity² = mass x height x gravitational field strength" becomes " 0.5 x velocity² = height x gravitational field strength". Since all the riders had the same initial vertical height and the same gravitational field strength, they would have the same final velocity. Small variations would be due to air resistance / friction.
84
What factors can affect the stopping distance?
* Mass of vehicle
* Speed of vehicle
* Antecedent Conditions
* Vehicle Condition
* Alcohol / Drugs
