Work, Energy And Momentum

Question 1

When a force moves an object, what is transferred and what is done?

Answer 1

Energy is transferred

And work is done

Question 2

What’s the unit for work and energy

Answer 2

Joule(J)

Question 3

What’s the equation for the work done? Give units

Answer 3

W(J) = F(N) x d(m)

Question 4

What happens if the distance moved is zero?

Answer 4

No work is done on the object.

Question 5

What does energy transferred equal?

Answer 5

Work done

Question 6

What is the work done on an object if a force of 300 N movies it a distance of 8m?

Answer 6

2400J

Question 7

The GPE of an object depends on what?

Answer 7

On it’s weight and how far it moves vertically

Question 8

How can the change in GPE be calculated ?

Answer 8

Ep= mxgxh

Question 9

What is the increase in Ep when a mass of 40kg is lifted 8m vertically?

Answer 9

320J

Question 10

What is power?

Answer 10

The rate of transfer of energy

Question 11

How can power be calculated?

Answer 11

P(W) = E(J) /t(s)

Question 12

The kinetic energy of a moving object depends on?

Answer 12

It’s mass and speed

Question 13

How can kinetic energy be calculated?

Answer 13

E(J) = 1/2 x m x v2

Question 14

A boy of mass 40kg runs at a speed of 5m/s. What is his kinetic energy?

Answer 14

500J

Question 15

When a spring is squashed and release it warms up. Why?

Answer 15

Some elastic potential energy is transferred by heating.

Question 16

What happens if an elastic band is stretched and released?

Answer 16

Elastic potential energy is transferred to kinetic energy.

Question 17

What do all moving objects have?

Answer 17

Momentum

Question 18

The greater the mass and the greater the velocity of an object, the greater it’s ….?

Answer 18

Momentum

Question 19

When do objects have momentum

Answer 19

When they’re moving

Question 20

How can momentum be calculated give units.

Answer 20

p(kgm/s) = m x v

Question 21

What’s the momentum of a 1000 kg car travelling at 30m/s?

Answer 21

30,000 kgm/s

Question 22

What does the conservation of momentum state?

Answer 22

When objects collide the total momentum before is equal to the total momentum after.

Question 23

Two students on roller skates stand holding each other in the playground. They push each other away. What can you say about the momentum of each student?

Answer 23

It is equal and opposite

Question 24

When two objects push each other apart, they move apart :?

Answer 24

With different speeds- if they have unequal masses

Equal and opposite momentum so their momentum is zero

Question 25

What happens when two vehicles collide?

Answer 25

They exert equal and opposite forces on each other.

Their total momentum is unchanged.

Question 26

What is impact time?

Answer 26

Time taken for collision to take place.

Question 27

Why do cars have crumple zones at both the front and the rear?

Answer 27

Cars may be hit from either the front or the rear in either case the crumple zone reduces the forces on the car. Or increases the impact the time.

Question 28

What do seat belts and airbags do?

Answer 28

Spread the force across the chest, and they also increase the impact time.

Question 29

What happens to a passenger if they’re wearing a very narrow seat belt?

Answer 29

The narrow seatbelt would not spread the force across the passengers body and might cut them.

Question 30

Whenever an object starts to move what must have been applied to it?

Answer 30

A force