Motion and Forces Flashcards
(113 cards)
1
Q
In a distance time graph what does it mean if the line is moving at a constant speed in a straight line that slips upwards?
A
It is moving at a constant speed
2
Q
What does the gradient of a distance-time graph show?
A
Represents the objects speed
3
Q
How can you tell velocity from speed?
A
Velocity is speed in a given direction
4
Q
How can you tell from a distance time graph that the object is stationary?
A
Stationary is a horizontal line
5
Q
Unit of acceleration?
A
m/s (squared)
6
Q
What does the area under the line on a velocity time graph represent?
A
The distance travelled
7
Q
If the velocity time graph is a horizontal line what is the acceleration?
A
0 acceleration
8
Q
What can forces do?
A
A force can change the shape of an object or its state
9
Q
What’s the unit for force?
A
N (Newtons)
10
Q
If the resultant force on an object is zero what happens?
A
The object stays at a constant velocity
11
Q
If the resultant force on an object is not zero what happens?
A
The velocity of the object will change
12
Q
What is acceleration?
A
The change in velocity (speed) per second
13
Q
What is the driving force ( engine force/motive force) down to?
A
It is due to friction between the ground and the tyre of each drive wheel
14
Q
What is the resultant force?
A
A single force that has the same effect as all the forces acting on an object
15
Q
What happens if the resultant force of an object isn’t zero?
A
The velocity will change
16
Q
When does the velocity of an object increase ? What type of acceleration is it ?
A
If the resultant force is in the same direction as the velocity it increases
Positive acceleration
17
Q
When does the velocity of an object decrease ? What type of acceleration is it ?
A
If the resultant force is in the opposite direction as its velocity
Negative acceleration
18
Q
If the resultant force is big what happens to the acceleration?
A
The acceleration is greater
19
Q
If the mass of an object is great what happens to the acceleration?
A
It is smaller for a given force
20
Q
What two forces are opposite to the driving force of a car?
A
Friction
Air resistance
21
Q
What two factors affect the stopping distance?
A
Thinking distance
Braking distance
22
Q
What is the thinking distance?
A
The distance travelled by the vehicle in the time it takes the driver to react
23
Q
What factors increase the thinking distance?5
A
Tiredness
Alcohol
Drugs
Mobile phone use
Increasing the speed
24
Q
How can you work out the thinking distance?
when you are given the drivers reaction time and speed
A
cars speed x reaction time
25
What is the breaking distance?
The distance travelled by the vehicle during the time the braking force acts
26
What increases the breaking distance?
Poor weather conditions
Poor car maintenance e.g. Worn tires
If the speed increases
27
What is the weight of an object?
The force of gravity on it
28
What do weight measured in?
N
29
What is mass?
The quantity of matter in it
30
What is mass measured in?
KG
31
How much gravitational field strength does the earth have?
Roughly 10 N/Kg
32
What is the unit of gravitational field strength?
N/Kg
33
What increases drag force?
Speed
34
What happens when an object falls in a fluid?
The fluid drags on the object
35
What happens when an object falls through the air?
The drag force is air resistance
36
What happens to the acceleration of an object and why?
The acceleration of the object decreases as it falls
because the drag force increases as it speeds up
37
When does an object reach a constant velocity (speed)? & what is its name?
When the drag force on it is equal and opposite to the weight
Terminal velocity
38
If the resultant force is zero what is the acceleration?
Zero too
39
What type of component shows a change in temperature?
A thermistor
40
Why would the current passing through each element be the same?
It is a series circuit and therefore the current is the same throughout
41
Because of forces, explain why the parachutist reached a terminal velocity and why opening the parachute reduces the terminal velocity?
1 when he left the airplane the force acts downwards
2 as the parachutist falls air resistance acts upwards
3 the weight is greater than the air resistance
4 as the velocity and speed equal eachother he reached terminal velocity
5 opening the parachute increased his surface area increasing the air resistance
6 air resistance is greater than the weight
7 the resultant forces slow down and when they are equal he reaches terminal velocity
42
What does the mass of an object have to do with its acceleration?
The greater the mass the smaller acceleration
43
What are the opposite forces of the driving force of a car?
Friction and air resistance
44
What is the unit of gravitational field strength?
N/kg
45
What increased drag force?
Speed
46
When an object falls through the air what force is acting on it?
Air resistance
47
When an object falls describe the torces?
The drag force increase as it speed up
| Acceleration decreases
48
When the drag force is equal and opposite to the weight what happens?
Terminal velocity : the resultant force is zero so the acceleration is 0
49
What name is given to the constant speed?
Terminal velocity
50
Why would it be good for electricans to wear rubber soled boots?
Increases overall resistances
| So gives a smaller current in the event of electric shock
51
When will the resultant force acting on an object cause an object to move?
When it is not zero the object will accelerate in the direction of the force
52
What happens if the result force acting on a stationary object is zero?
It will remain stationary
53
What happens if the resultant force acting on a moving object is zero?
The object will continue to move at the same speed and in the same direction
54
What is acceleration measured in?
m/s2
55
What determines the acceleration of the object?
The resultant force acting on it
| The mass of it
56
What are most resistive forces caused by?
Air resistance
57
What is happening (in terms of force) when a vehicle travels at a steady speed?
The resistive forces balance the driving force
58
What does an increased speed do to the breaking force needed?
Increase it
59
If you are given braking force, what does increased speed so to the stopping distance?
Increases it
60
What is the stopping distance?
Thinking distance add braking distance
61
What is thinking distance?
The sum of the distance the vehicle travels during the drives reaction time
62
What is the braking distance?
The distance the car travels under the braking forc
63
What is braking distance affected by?
Poor condition of car brakes or three
| Wet or icy weather or road conditions
64
Describe the process of breaking?
In terms of energy and force.
When brakes applied,
The friction force between the brakes and the wheel
Reduces the kinetic energy of the vehicle
The temperature of the brakes increase
65
In a fluid, as speed increases, what happens to frictions?
The greater the frictional force that acts on it
66
Describe what happens when an object falls through a liquid?
It initially accelerates due to the force of gravity
Eventually, the resultant force will be zero
The object will move at its terminal velocity (constant speed)
67
What is gravitational field strength measured in?
N/kg
68
What happens if force is applied to an elastic object?
The object stretches
| And stores elastic potential energy
69
What is Spring constant measured in?
N/m
70
What is the extension of an elastic object directly proportional to?
(Given the limit of proportionality is not exceeded)
The force applied
71
What is work done measured in?
J
72
How can long distance vehicles check that their drives don't drive for too long?
Tachographs
73
What is deceleration?
Negative acceleration
74
What forces act when a crate is pushed along the floor?
```
Push force (as a person exerts force on crate)
Friction (between the floor and the crate)
```
75
When a crate is pushed along the floor, when will the resultant velocity be zero?
When it is pushed at a constant velocity
Push force on the crate is equal in size but acts in the opposite direction to the force of friction of the floor on the crate
76
Describe the forces of a jet plane taking off?
The thrust force (engine force) of the engine is GREATER than the force of air resistance (drag force) on it
Resultant force on it is different to the thrust force and the force of air resistance
Resultant force is therefore not zero
Greater the force the quicker the takeoff
77
Describe the force changes when a car drives applies the brakes?
The braking force is greater than the force from the engine
Resultant force is different between braking and engine force
Breaking force acts in the opposite direction
So it slows the car down
78
If an object is acted on by two unequal forces acting in opposite directions, what is the resultant force?
Equal to the difference between the two forces
| In the direction of the larger force
79
When does velocity decrease?
The resultant force is in the opposite direction to its velocity
80
When does velocity increase?
If the resultant force is in the same direction as the velocity
81
What are the resistive forces acting on a car?
Friction (between parts of the car and the tyre and road) and air resistance
82
What does the accelerator pedal do?
Varies the driving force
83
What is the stopping distance?
The shortest distance a vehicle can safely stop in
84
Things that affect thinking distance?
Tiredness
Alcohol
Drugs
Mobile phones
Increase reaction times
85
Things that affect breaking distance?
Poorly maintain vehicles - longer to stop as brakes and tyres are less effective eg worn brakes or tyres
Adverse road conditions - brake with less force to avoid skidding eg icy or wet roads
Faster a vehicle is travelling - further it travels before it stops
86
What affect both thinking and stopping distance?
Speed of vehicle
87
What happens when an object is released above ground and falls?
It accelerates downwards at a constant acceleration of 10 m/s2
Acceleration due to gravity
88
What happens if an object falls with no other forces acting on it?
The resultant force on it is its weight
89
How is drag force increased?
Speed
90
Describe the changes in forces and velocity as an object falls through a liquid?
Acceleration decreases as it falls
As drag force increases as it speeds up
Resultant force decreases so acceleration decreases
Reaches terminal velocity when drag force equals its weight
Resultant force is zero so the acceleration is zero
91
When does a parachutist reach terminal velocity?
Drag force equals force of gravity
92
How do anti skid surfaces work?
They increase the friction between the vehicle and the grounds so that more force can be applied without skidding happening
So stopping distance is reduced
93
When a vehicle is travelling at high speed what force is greater?
Air resistance (drag force)
94
How do wind deflectors work?
Reduce air resistance on vehicle
So less engine force and power needed to maintain a speed
Fuel costs reduced
(As speed increases so does air resistance)
95
Describe how skidding happens?
Brakes applied with too much force
| Wheels lock and tyres slid on the road as a result
96
What does an LED do?
Emits light when a current passes through it
97
What does a diode do?
Allows current to move only in one direction
98
What does a resistor do?
Limits the current in a circuit
99
What does a variable resistor do?
Allows the current to be varied
100
What does a fuse do?
Melts and breaks the circuit if the current through it is greater than a certain amount
101
What does a cell (battery) do?
A cell is necessary to push electrons around a complete circuit
A battery consists of two or more cells
102
What does an indicator do?
Emits light as a signal when a current passes through it
| Or as a light source such as a bulb
103
Why does resistance in a metal increase as temperature increases?
The ions in metal vibrate more
| So they twist the passage of electrons through the filament more
104
Why is the force needing to pull a boat force is greater than the resultant force?
Resistant forces are needed to overcome
105
When potential difference increases, why would the resistance of a bulb increase?
Temperature of bulb increases
106
Why do control rods reduce the amount of energy released each second from a nuclear fuel?
They absorb excess neutrons
So there are fewer chain reactions
Chain reactions slow down
107
Why does applying the breaks on a car cause the temperature to increase?
Friction between the brakes and the whelk
| Decrease in kinetic energy and increase in thermal energy
108
Describe why a cyclist would rapidly accelerate then at a lower acceleration?
Forward force more than air resistance
Velocity increased
Air resistance increases (as speed increases)
Resultant force decreases
Cyclist still accelerates with less velocity
109
WHAT CAUSES AIR RESISTANCE TO INCREASE
MORE VELOCITY
110
What causes a cyclist to gradually reach terminal velocity?
```
Air resistance increase
Velocity decrease
Forces become equal
Zero resultant force
Zero acceleration
Terminal velocity
```
111
What happens to the breaks when the kinetic energy of the bike decrease?
Temperature increases
112
Describe the general for anything that becomes charged?
Friction between objects
| Charge transfers between objects
113
What is an ion?
An atom that has lost/gained electrons
