P2.2

Question 1

What can a force do?

Answer 1

It can change the shape of an object or change its state of rest or its motion.

Question 2

What happens when two objects push or pull on each other?

Answer 2

They exert equal and opposite forces on one another.

Question 3

What happens to the forces to pull a tractor out of the mud?

Answer 3

The force of the ground on the tractor needs to be greater than the force of the mud on the car.

Question 4

What is the motive force?

Answer 4

Driving force on a farthest makes it move.

Question 5

What causes the motive force?

Answer 5

The friction between the ground and the tyres.

Question 6

Where does friction occur?

Answer 6

Where the two objects are in contact.

Question 7

What happens when the resultant force is zero?

Answer 7

• remains stationary

- continues to move at a constant speed in the same direction

Question 8

What is a resultant force?

Answer 8

A single force.

Question 9

What happens when the resultant force is not zero?

Answer 9

The movement of the car depends on the size and direction of the resultant force.

Question 10

What happens to the resultant force if an object is acted on by two unequal forces acting in opposite directions?

Answer 10

• it’ll be equal to the difference between the two forces

- it’ll be in the direction of the larger force

Question 11

What is the equation for resultant force?

Answer 11

=mass (kg) X acceleration (m/s2)

Question 12

What are forces measured in?

Answer 12

Newtons.

Question 13

What happens if a velocity increases?

Answer 13

The resultant force is in the same direction as the velocity.

Question 14

What happens if the velocity decreases?

Answer 14

The resultant force is opposite in direction to its velocity .

Question 15

What happens if the driver presses harder on the accelerator?

Answer 15

It varies the driving force of the engine.

Question 16

What does the braking force needed to stop a vehicle in a certain distance depend on?

Answer 16

• the speed of the vehicle when brakes are applied

- the mass of the vehicle

Question 17

What is the stopping distance affected by?

Answer 17

Braking and thinking distance.

Question 18

What is the equation for the stopping distance?

Answer 18

= thinking distance + braking distance

Question 19

What is the thinking distance?

Answer 19

Distance travelled by the vehicle in the time it takes the driver to react.

Question 20

What is the braking distance?

Answer 20

Distance travelled by the vehicles once the brakes have been applied.

Question 21

What affects the stopping distance?

Answer 21

• tiredness,alcohol,drugs
• speed vehicle is travelling at
• road conditions
• poorly maintained vehicles

Question 22

What is the weight of an object?

Answer 22

Force of gravity on it.

Question 23

What is the mass of an object?

Answer 23

Quantity of matter in it.

Question 24

What is the equation for weight?

Answer 24

=mass (kg) X gravitational field strength (N/kg)

Question 25

What is the resultant force if an object falls with no other forces acting on it?

Answer 25

The resultant force on it is its weight.

Question 26

What happens if an object falls in a fluid?

Answer 26

The fluid drags on the object.

Question 27

What is terminal velocity?

Answer 27

When an object reaches a constant speed and the drag force is equal and opposite to its weight.

Question 28

What is air resistance?

Answer 28

Drag force when an object is moving through air.

Question 29

What happens to an elastic object when the forces deforming it are removed?

Answer 29

It regains its original shape.

Question 30

What is the extension?

Answer 30

The increase of length from its original shape.

Question 31

What is the equation for the extension?

Answer 31

=extension - original length

Question 32

What happens when an elastic object is stretched?

Answer 32

The elastic potential energy is stored in the object.

Question 33

What happens when the stretching force is removed?

Answer 33

The elastic energy stored in the object is released.

Question 34

Why does an object stretch more than predicted?

Answer 34

It has been stretched beyond its limit of proportionality.

Question 35

What is Hooke's law?

Answer 35

The extension is directly proportional to the force applied to it, provided its limit of proportionality is not exceeded.

Question 36

What is the equation to Hooke's law?

Answer 36

force applied(N)=Spring constant(N/m) X extension(m)

Question 37

What is the spring constant equal to?

Answer 37

The force per unit extension needed to extend the spring.

Question 38

Why does reducing the speed reduce the fuel it uses?

Answer 38

Because air resistance at high speed is greater than at low speed so more fuel is used.

Question 39

How can drivers reduce their fuel usage? How?

Answer 39

By fitting a wind deflector over the cab. | Reduces the air resistance.

Question 40

Name 2 ways that have reduced speeding:

Answer 40

- speed cameras | - anti-skid surfaces