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9th Physics > Work And Energy > Flashcards

Work And Energy Flashcards

(86 cards)

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1
Q

What is the formula for calculating work done?

A

Work done = Force × Displacement × cos(θ)

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2
Q

What unit is work measured in?

A

Joules (J)

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3
Q

True or False: Work is done only when a force causes displacement.

A

True

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4
Q

Fill in the blank: If the angle between the force and displacement is 90 degrees, the work done is _____ .

A

zero

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5
Q

What is kinetic energy?

A

Kinetic energy is the energy possessed by an object due to its motion.

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6
Q

What is the formula for kinetic energy?

A

Kinetic Energy = 1/2 × mass × velocity²

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7
Q

What is potential energy?

A

Potential energy is the energy possessed by an object due to its position or configuration.

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8
Q

What is the formula for gravitational potential energy?

A

Potential Energy = mass × gravity × height

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9
Q

What is the SI unit of energy?

A

Joule (J)

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10
Q

True or False: Energy can be created and destroyed.

A

False

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11
Q

What is the Law of Conservation of Energy?

A

Energy cannot be created or destroyed; it can only be transformed from one form to another.

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12
Q

What type of energy is stored in a compressed spring?

A

Elastic potential energy

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13
Q

Fill in the blank: The work done is _____ when the force is applied in the opposite direction to the displacement.

A

negative

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14
Q

What is the relationship between work and energy?

A

Work is done when energy is transferred or transformed.

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15
Q

What is mechanical energy?

A

Mechanical energy is the sum of kinetic and potential energy in a system.

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16
Q

What is the formula for total mechanical energy?

A

Total Mechanical Energy = Kinetic Energy + Potential Energy

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17
Q

True or False: A stationary object has kinetic energy.

A

False

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18
Q

What happens to the potential energy of an object as it falls?

A

It decreases as kinetic energy increases.

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19
Q

Fill in the blank: Work done against gravity is equal to the change in _____ energy.

A

potential

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20
Q

What is power?

A

Power is the rate at which work is done or energy is transferred.

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21
Q

What is the formula for power?

A

Power = Work done / Time taken

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22
Q

What unit is power measured in?

A

Watt (W)

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23
Q

True or False: One watt is equivalent to one joule per second.

A

True

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24
Q

Fill in the blank: The work-energy theorem states that the work done on an object is equal to the change in its _____ energy.

A

kinetic

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25
What is the effect of friction on work done?
Friction reduces the amount of work done by opposing the motion.
26
What is the gravitational force acting on a 10 kg object near the Earth's surface?
Approximately 98 Newtons (using g = 9.8 m/s²)
27
Fill in the blank: The energy possessed by a body at rest is called _____ energy.
potential
28
What is the relationship between work and displacement?
Work is directly proportional to displacement when force is constant.
29
True or False: An object moving at a constant speed has no net work done on it.
True
30
What are the two main forms of mechanical energy?
Kinetic energy and potential energy
31
What happens to total mechanical energy in a closed system?
It remains constant.
32
What is an example of a situation where work is done?
Lifting a box off the ground.
33
Fill in the blank: The energy of an object due to its position is called _____ energy.
potential
34
What is the work done if a force of 10 N moves an object 5 m in the direction of the force?
50 Joules
35
True or False: Work done can be negative, positive, or zero.
True
36
What does it mean if the work done is zero?
There is no displacement in the direction of the applied force.
37
What is the effect of doubling the velocity of an object on its kinetic energy?
It increases the kinetic energy by a factor of four.
38
What does the term 'efficiency' refer to in the context of work and energy?
Efficiency refers to the ratio of useful work output to total work input.
39
What is the formula for calculating efficiency?
Efficiency = (Useful work output / Total work input) × 100%
40
What is a common example of potential energy?
Water stored in a dam.
41
Fill in the blank: The work done by a force is maximum when the angle between the force and displacement is _____ degrees.
zero
42
What is the principle of conservation of mechanical energy?
In the absence of non-conservative forces, the total mechanical energy remains constant.
43
What is the formula for work done?
Work done = Force x Distance x cos(θ)
44
If a force of 10 N moves an object 5 m in the direction of the force, what is the work done?
50 Joules
45
True or False: Work is a scalar quantity.
True
46
What unit is work measured in?
Joules (J)
47
Fill in the blank: Work done is positive when the angle θ is __________.
less than 90 degrees
48
What is the work done when a force of 20 N moves an object 0 m?
0 Joules
49
If a force of 15 N is applied at an angle of 60 degrees to the direction of motion, what is the work done moving an object 10 m?
75 Joules
50
What is kinetic energy?
Kinetic energy is the energy possessed by an object due to its motion.
51
What is the formula for kinetic energy?
Kinetic Energy = 1/2 mv²
52
Calculate the kinetic energy of a 2 kg object moving at a speed of 3 m/s.
9 Joules
53
True or False: Potential energy is energy due to position.
True
54
What is the formula for gravitational potential energy?
Potential Energy = mgh
55
If a 5 kg object is raised to a height of 10 m, what is its potential energy?
490 Joules
56
Fill in the blank: The SI unit of energy is __________.
Joule (J)
57
What is the work-energy theorem?
The work done on an object is equal to the change in its kinetic energy.
58
If an object's kinetic energy increases from 20 J to 50 J, how much work was done?
30 Joules
59
True or False: Energy can be created and destroyed.
False
60
What is the law of conservation of energy?
Energy cannot be created or destroyed, only transformed from one form to another.
61
Calculate the work done when a 30 N force pulls an object 4 m at an angle of 0 degrees.
120 Joules
62
What is the relationship between work and energy?
Work done is equal to the change in energy.
63
If 100 J of work is done on an object, what is the change in its energy?
100 Joules
64
Fill in the blank: The energy possessed by an object due to its motion is called __________.
kinetic energy
65
What happens to the kinetic energy of an object if its speed doubles?
The kinetic energy increases by a factor of four.
66
What is the potential energy of a 10 kg object at a height of 5 m?
490 Joules
67
Calculate the work done when lifting a 5 kg object to a height of 2 m.
98 Joules
68
True or False: Work can be done against gravity.
True
69
If a car does 200 J of work in moving uphill, what is the work done against gravity?
200 Joules
70
What is the gravitational force acting on a 1 kg mass near the Earth's surface?
9.8 N
71
Fill in the blank: The work done by a variable force can be calculated using __________.
integration
72
What is the total mechanical energy of an object?
The sum of its kinetic and potential energy.
73
If an object has 30 J of kinetic energy and 70 J of potential energy, what is its total mechanical energy?
100 Joules
74
True or False: An object at rest has kinetic energy.
False
75
Calculate the work done if a force of 50 N moves an object 2 m in the opposite direction.
-100 Joules
76
What is the work done when a 25 N force is applied at an angle of 90 degrees to the direction of motion?
0 Joules
77
What is the potential energy of a 3 kg object at a height of 4 m?
117.6 Joules
78
Fill in the blank: The unit of power is __________.
Watt (W)
79
If a machine does 400 J of work in 20 seconds, what is its power?
20 Watts
80
True or False: Power is the rate at which work is done.
True
81
What is the formula for calculating power?
Power = Work done / Time taken
82
Calculate the power if 300 J of work is done in 15 seconds.
20 Watts
83
What is the relationship between work, energy, and power?
Power is the rate of doing work or transferring energy.
84
If a 10 kg object is dropped from a height of 10 m, what is its potential energy at the top?
980 Joules
85
What is the work done by a force that moves an object 10 m with a force of 10 N in the direction of motion?
100 Joules
86
Fill in the blank: The energy stored in an object due to its position is called __________.
potential energy

9th Physics (1 decks)

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