Forces and Motion

Question 0

What is acceleration?

Answer 0

Change in velocity per second

Question 1

What are long vehicles fitted with to ensure they don’t drive too long?

Answer 1

A tachograph

Question 2

What does the area under a velocity-time graph represent?

Answer 2

Distance

Question 3

A force can change…?

Answer 3

The shape of an object or it’s state of motion

Question 4

What force on a car makes it move?

Answer 4

The driving force (sometimes called the engine force or motive force). This is due to friction between the ground and the tyre on each drive wheel

Question 5

What two forces are always acting on you?

Answer 5

Gravity and the force supporting you

Question 6

What the resultant force on an object is zero…?

Answer 6

It will remain stationary if it was at rest or continue to move at the same velocity if it was already moving

Question 7

Resultant force = mass x ?

Answer 7

Acceleration

Question 8

For any car travelling at a constant velocity, the resultant force is?

Answer 8

Zero, because the force of the engine is balanced by the resistive forces (friction, air resistance and friction between parts of the car)

Question 9

How does a driver vary the driving force or a vehicle?

Answer 9

Using the accelerator

Question 10

The breaking force needed to stop a vehicle depends on…?

Answer 10

The speed of the vehicle when the brakes are first applied and the mass of the vehicle

Question 11

Thinking distance is equal to?

Answer 11

Car speed x driver’s reaction time.

Stopping distance is equal to this plus braking distance.

Question 12

Factors affecting stopping distance include?

Answer 12

Tiredness, alcohol, distractions, road conditions and the maintenance of the vehicle

Question 13

The weight of an object is the force of gravity on it.

Answer 13

The mass (kg) is the quantity of matter

Question 14

Gravitational field strength is measured in…?

Answer 14

N/kg.

Weight = mass x gfs

Question 15

When we release an object above the ground, it falls because of it’s weight (force of gravity). If it has no other force acting on it, it’s weight is it’s resultant force. It accelerates downwards at a constant acceleration due to gravity. Air resistance is very small in a short descent so it is often ignored.

Answer 15

Yes.

Question 16

If an objects falls in a fluid, the fluid drags on the object. The drag force increases with speed so the acceleration decreases as it falls and the resultant force decreases. It reaches terminal velocity when the resultant force is zero.

Answer 16

Yes.

Question 17

Why is a squash ball elastic?

Answer 17

It regains it’s original shape

Question 18

The extension of a steel spring is directly proportional to the weight hung on it. Who’s law is this?

Answer 18

Hooke’s Law

Question 19

A rubber band will not give a straight line, nor will a polythene strip because it stretches very little at first, the ‘gives’ and stretches easily.

Answer 19

Yes.

Question 20

When an object is stretched, which sort of energy is stored in it because work has been done on it?

Answer 20

Elastic potential energy

Question 21

If the force on a steel spring becomes too large, it will go beyond the limit of proportionality. Otherwise, the extension of the spring is directly proportional to the force applied to it. Any object that acts the same way obeys Hooke’s law. The rubber band and polythene strip have a very low limit of proportionality.

Answer 21

Yes.

Question 22

The stiffer a spring is, the greater the…?

Answer 22

Spring constant

Question 23

Reducing the speed of a vehicle will reduce the amount of fuel is uses. Why?

Answer 23

The resistance at high speed is much greater than that at low speed. Lorry drivers can fit a wind deflector over the can to reduce air resistance so less fuel is needed to maintain a certain speed

Question 24

Speed limits vary on the motorway according to what?

Answer 24

How much traffic there usually is

Question 25

If you are caught speeding, you can be fined or lose your licence. In some areas, residents are supplied with mobile speed cameras. Some say this is to increase the council's income.

Answer 25

Yes.

Question 26

At traffic lights there are anti-skid surfaces with rougher surfaces. What is their purpose?

Answer 26

To increase friction between the surface and a vehicle tyre to reduce the chance of skidding when the driver applies the brakes

Question 27

Skidding happens when...?

Answer 27

Brakes are applied to harshly, causing the wheels to lock and the tyres to slide on the road

Question 28

When an object is moved by a force, we say what is done?

Answer 28

Work

Question 29

Energy transferred to an object = amount if work done. What does work done equal?

Answer 29

Force applied x distance moved in the direction of the force

Question 30

Most of the work done to overcome friction is transferred to which type of energy?

Answer 30

Heat

Question 31

When you lift something up, your muscles transfer chemical energy into...?

Answer 31

Gravitational potential energy

Question 32

Gravitational potential energy is energy stored in an object because if its position in the Earth's gravitational field. When an object is moved up, the GPE...?

Answer 32

Increases

Question 33

Work done when an object moves up or down depends on...?

Answer 33

How far it is moved vertically and it's weight

Question 34

Kinetic energy is equal to...?

Answer 34

1/2mv^2

Question 35

Kinetic energy recovery systems do what in a car?

Answer 35

Story kinetic energy when the vehicle brakes to use later on

Question 36

Hybrid cars use electric generators to transfer kinetic energy into electrical energy which is stored in the battery.

Answer 36

Yes.

Question 37

Elastic potential energy is the energy stored in an elastic objects when...?

Answer 37

Work is done to change its shape.Lots of this energy is turned into kinetic energy when the material regains its shape.

Question 38

Momentum is equal to...?

Answer 38

Mass x velocity

Question 39

If two trolleys of the same mass crash together, the velocity of trolley A is halved by the impact and the combined mass is twice that as before the collision. So momentum stays the same. This applies to any closed system (where no resultant forces are acting). The total momentum before an event is equal to the total momentum after an event.

Answer 39

Yes.

Question 40

If two single trolleys travel equal distances in the same time they recoil at equal speeds when they collide. If a double trolley only travels half the speed of a single trolley, the speed is half that of the single trolley. In both occasions, momentum is the same and they recoil in opposite directions.

Answer 40

Yes.

Question 41

The total momentum before and after an explosion is...?

Answer 41

The same

Question 42

An artillery gun of mass 2000kg fires a shell of mass 20kg at a velocity of 120m/s. What is the recoil velocity of the gun?

Answer 42

20 x 120 = 2000 x ? 2400 = 2000 x 1.2 Recoil velocity = 1.2m/s

Question 43

What are crumple zones at the front and rear ends of a car designed to do?

Answer 43

Lessen the force of an impact. READ NOTES ON THIS.

Question 44

A seatbelt acts across the chest. What is the purpose of this?

Answer 44

To spread out the force of a collision

Question 45

In a crash, cars have air bags which inflate to spread out the force of an impact across the upper part of the body which increases the impact time so the effect of the force is lessened.

Answer 45

Yes.

Question 46

Why do some car manufacturers not like having extra safety features on their cars?

Answer 46

They are expensive to produce