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Work, energy, Power Flashcards

1
Q

What will this chapter explain?

A

Work

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2
Q

What is the relationship between work

A

energy

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3
Q

What is work?

A

Work is said to be done whenever a force is applied to cause a body to move.

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4
Q

Give some examples of when work is done.

A

When you push a car

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5
Q

When is no work done?

A

When no movement takes place after applying a force.

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6
Q

If you carry a bag of palm kernels on your head while standing

A

is work done?

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7
Q

When is work said to be done?

A

When a force moves its point of application a distance in the direction of the force.

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8
Q

A force F moves a body a distance S in the direction of the force. What is the formula for work done?

A

W = F x S

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9
Q

Define work done.

A

The product of the force and the displacement in the direction of the force.

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10
Q

What is the unit of work?

A

Joule (J).

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11
Q

In what units must force and displacement be measured for work to be in joules?

A

Force in newtons

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12
Q

What is the formula for work done in lifting a body of mass ‘m’ through a height ‘h’ in the earth’s gravitational field?

A

W = mgh

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13
Q

What is the SI unit of work?

A

Joule (J)

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14
Q

What is 1 joule equal to?

A

1 newton-metre (1 Nm)

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15
Q

Is work a scalar or vector quantity?

A

Scalar

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16
Q

If both force and displacement are vector quantities

A

why is work a scalar quantity?

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17
Q

Define energy.

A

The capacity or ability to do work.

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18
Q

What is the SI unit of energy?

A

Joule (J).

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19
Q

Is energy a scalar or vector quantity?

A

Scalar.

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20
Q

Name the two types of mechanical energy.

A

Potential energy and kinetic energy.

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21
Q

Define potential energy (PE).

A

Energy possessed by a body by virtue of its position or state.

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22
Q

Give examples of potential energy.

A

A stone poised on a cliff

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23
Q

What is the formula for potential energy?

A

PE = mgh

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24
Q

Define kinetic energy (KE).

A

Energy possessed by a body by virtue of its motion.

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25
Give examples of kinetic energy.
A moving car
26
What is the formula for kinetic energy?
KE = 1/2 mv²
27
Define power.
The time rate of doing work.
28
Give other commonly used units of power.
Kilowatt (kW)
29
If two boys of the same weight climb a flight of steps of the same height
which boy has greater power?
30
Why does the boy that gets to the top first have greater power?
Because he has done the work of moving his weight through that height in a shorter time.
31
If work W joules is done in time t seconds
what is the formula for power?
32
If work is in joules and time is in seconds
what is the unit of power?
33
What is 1 watt equal to?
1 joule per second.
34
What are the conversions for 1 kW and 1 MW?
1 kW = 1000 W = 10³ W
35
What is the conversion for 1 horsepower (hp)?
1 hp = 746 W.
36
Define one kilowatt-hour.
The work done in one hour by an agent working at the constant rate of one kilowatt.
37
What does the discussion in the chapter indicate about work
potential energy
38
What can be used to change energy from one form to another?
Suitable machines.
39
What is the law that governs changes in forms of energy?
The law of conservation of energy.
40
State the law of conservation of energy.
In an isolated or closed system
41
What is an isolated or closed system?
A group of objects that neither receives energy from nor gives energy to objects outside the system.
42
Give an example of an isolated system.
The whole universe.
43
According to the law of conservation of energy
what is constant for a given body in terms of mechanical energy?
44
What changes can occur between potential and kinetic energy for a given body?
Energy may change from potential energy to kinetic or from kinetic to potential.
45
Give examples of energy conservation discussed in the text.
A falling body and the simple pendulum.
46
In the example of a falling body
what is the initial energy and what does it transform into?
47
At what point during a falling body's descent is the energy entirely kinetic?
At the ground level (R).
48
In a simple pendulum
where is the potential energy maximum?
49
In a simple pendulum
where is the kinetic energy maximum?
50
What is the energy transformation in a simple pendulum as it swings?
Potential energy transforms into kinetic energy as it moves towards the center
51
What are the two broad classes of energy resources?
Renewable and Non-Renewable.
52
Define renewable energy resources.
Energy resources that can be replaced as they are used and are continually replenished.
53
Give examples of renewable energy resources.
Solar energy
54
What is solar energy?
Energy available from the sun.
55
How is solar energy used?
Photosynthesis
56
What is wind energy used for?
Sailing ships and turning windmills.
57
What are examples of water energy use?
Modern dams and hydroelectric plants
58
What is biomass energy?
Energy from cornstalks
59
Define non-renewable energy resources.
Energy resources that are depleting and cannot be replenished as they are used.
60
Give examples of non-renewable energy resources.
Nuclear energy
61
What is nuclear energy used for?
Producing heat to operate turbines and drive ships and aircrafts.
62
What are examples of nuclear energy?
Fission and fusion energy.
63
What do petroleum and natural gas constitute?
The world's major energy resources.
64
What are fossil fuels?
Fuels like petroleum
65
What is a major consequence of using wood as an energy source in Nigeria?
Deforestation.

Physics (25 decks)

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