Topic 3: Work and Energy Flashcards

1
Q

What is work?

A

A measure of the energy transferred.

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2
Q

What is work measure in?

A

Joules (J)

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3
Q

What equation do you use to calculate work?

A

Work=force x distance

W=Fd

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4
Q

How can energy be lost?

A

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

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5
Q

What is gravitational potential energy?

A

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

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6
Q

What is the equation to work out gravitational potential energy?

A

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

PE=mgh

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7
Q

What is kinetic energy?

A

Movement energy.

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8
Q

What is kinetic energy measured in?

A

Joules (J)

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9
Q

What do all moving objects have?

A

Kinetic energy.

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10
Q

What is the equation to calculate kinetic energy?

A

Kinetic energy=1/2 x mass x velocity ²

KE=1/2mv²

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11
Q

How do you calculate total energy?

A

Gravitational potential energy + kinetic energy=total energy

PE+KE

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12
Q

What is elastic energy?

A

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

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13
Q

What is extension directly proportional to?

A

Force applied.

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14
Q

What is the limits of proportionality?

A

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

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15
Q

What is the spring constant?

A

The stiffness of the spring.

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16
Q

What is the spring constant measured in?

A

Newtons per metre N/m

17
Q

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

A

Force=spring constant x extension

F=kx

18
Q

How do you calculate elastic potential energy?

A

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

Ee=0.5 x k x e²

19
Q

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

A

The area under the force-extension graph.

20
Q

What is Hooke’s law?

A

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

21
Q

How do you reduce aerodynamic losses?

A

more streamlined designs.

22
Q

How do you reduce rolling resistance?

A

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

23
Q

What do stop- start systems reduce?

A

Idling losses.

24
Q

How do you reduced inertial losses?

A

Lighter cars.

25
Q

What is the equation used to describe hooks law?

A

F=kx

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

26
Q

When does Hooke’s equation not work?

A

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

27
Q

When does Hooke’s equation not work?

A

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

28
Q

When does Hooke’s equation not work?

A

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

29
Q

when 5 things make fuel consumption more prominent?

A
Uphill
Carrying large loads
High speed
Rough surfaces
Under-inflated tyres
30
Q

What are 3 car safety features?

A

Seat belts
airbags
crumple zones

31
Q

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

A

They increase the distance over which the energy is transferred.

32
Q

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

A

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

33
Q

How do seat belts work and what are they?

A

Strong belt of stretchy material.

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

34
Q

How do crumple zones work and what are they?

A

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).

35
Q

How do air bags work and what are they?

A

Bag inflates rapidly in front of a person during crash.

Acts as a cushion. slows passenger over longer period, reduces deceleration and force.

36
Q

Can energy be destroyed?

A

No it is always transferred from one form to another.