Topic 3: Work and Energy

Question 1

What is work?

Answer 1

A measure of the energy transferred.

Question 2

What is work measure in?

Answer 2

Joules (J)

Question 3

What equation do you use to calculate work?

Answer 3

Work=force x distance

W=Fd

Question 4

How can energy be lost?

Answer 4

Can be lost as heat to the surroundings by air resistance and friction.

Question 5

What is gravitational potential energy?

Answer 5

The energy stored in an object as the result of its vertical piston or height.

Question 6

What is the equation to work out gravitational potential energy?

Answer 6

Gravitational potential energy=mass x gravitational field strength x change in height

PE=mgh

Question 7

What is kinetic energy?

Answer 7

Movement energy.

Question 8

What is kinetic energy measured in?

Answer 8

Joules (J)

Question 9

What do all moving objects have?

Answer 9

Kinetic energy.

Question 10

What is the equation to calculate kinetic energy?

Answer 10

Kinetic energy=1/2 x mass x velocity ²

KE=1/2mv²

Question 11

How do you calculate total energy?

Answer 11

Gravitational potential energy + kinetic energy=total energy

PE+KE

Question 12

What is elastic energy?

Answer 12

When an object is stretched or squashed, it stores elastic potential energy. (When you stretch a spring)

Question 13

What is extension directly proportional to?

Answer 13

Force applied.

Question 14

What is the limits of proportionality?

Answer 14

When the spring will not return back to its original length if you take away the force.

Question 15

What is the spring constant?

Answer 15

The stiffness of the spring.

Question 16

What is the spring constant measured in?

Answer 16

Newtons per metre N/m

Question 17

What is the equation to calculate the force of storing energy in springs?

Answer 17

Force=spring constant x extension

F=kx

Question 18

How do you calculate elastic potential energy?

Answer 18

Elastic potential energy= 1/2 x spring constant x extension ²

Ee=0.5 x k x e²

Question 19

How do you measure the work done stretching/compressing a spring?

Answer 19

The area under the force-extension graph.

Question 20

What is Hooke’s law?

Answer 20

The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.

Question 21

How do you reduce aerodynamic losses?

Answer 21

more streamlined designs.

Question 22

How do you reduce rolling resistance?

Answer 22

having correctly inflated tyres / using materials which don’t heat up as much as they are squashed.

Question 23

What do stop- start systems reduce?

Answer 23

Idling losses.

Question 24

How do you reduced inertial losses?

Answer 24

Lighter cars.

Question 25

What is the equation used to describe hooks law?

Answer 25

F=kx | Force(N) = spring constant(N/m) x the extension(m)

Question 26

When does Hooke's equation not work?

Answer 26

When the elastic limit has been exceeded. (limit of proportionality)

Question 27

When does Hooke's equation not work?

Answer 27

When the elastic limit has been exceeded. (limit of proportionality)

Question 28

When does Hooke's equation not work?

Answer 28

When the elastic limit has been exceeded. (limit of proportionality)

Question 29

when 5 things make fuel consumption more prominent?

Answer 29

``` Uphill Carrying large loads High speed Rough surfaces Under-inflated tyres ```

Question 30

What are 3 car safety features?

Answer 30

Seat belts airbags crumple zones

Question 31

In terms of work done, how do air bags and crumple zones reduce the force on the driver?

Answer 31

They increase the distance over which the energy is transferred.

Question 32

In terms of momentum, how do air bags and crumple zones reduce the force on the driver?

Answer 32

Slow the car and passenger as gradually as possible; deceleration decreases (which will decrease the force).

Question 33

How do seat belts work and what are they?

Answer 33

Strong belt of stretchy material. | Prevents the person being thrown forward in a crash and stretchy material absorbs some of the energy.

Question 34

How do crumple zones work and what are they?

Answer 34

Section at front and back of the car designed to crumple on impact. Slows car over longer period so it decreases the deceleration (which decreases the force).

Question 35

How do air bags work and what are they?

Answer 35

Bag inflates rapidly in front of a person during crash. | Acts as a cushion. slows passenger over longer period, reduces deceleration and force.

Question 36

Can energy be destroyed?

Answer 36

No it is always transferred from one form to another.