Energy and work

Question 1

What is energy?

Answer 1

Energy is the ability to do work.

It is also considered the ‘measurement’ of the ability to do work.

Question 2

What is Kinetic energy?

Answer 2

Kinetic energy is a type of energy that is associated with the motion of an object.

Question 3

Thermal energy?

Answer 3

Energy related to heat

Question 4

List as many types of energy as you can

Answer 4

Thermal
Light
Gravitational Potential
Kinetic
Electrical
Chemical

Question 5

What is the SI unit for energy?

Answer 5

The SI unit for energy is Joules

Question 6

What is work? Define work.

Answer 6

‘work’ is the transfer of energy when an object is displaced by an external force

Work is also known as the transfer of mechanical energy.

Question 7

What is the formula for work?

Answer 7

Work = Force x Displacement x cos theta

w = fs x cos(theta)

OR w=fs x cos(Theta) –> not scientifically correct

Question 8

When is work done?

Answer 8

Work is done when force is applied to an object and thus results in displacement.

Work is also done when there is a change in energy

Question 9

Is work a scalar or a vector quantity? Why?

Answer 9

Work is a scalar quantity as it deals with energy and the transfer of mechanical energy. Even though displacement is associated with work, it is not considered to be a vector quantity.

Energy is a scalar quantity and has no direction associated with it. Therefore, when calculating ‘work,’ the only thing that matters is the magnitude

Question 10

What is the formula for kinetic energy?

Answer 10

1/2 x mass x velocity squared

Question 11

What is the change in kinetic energy? This is also known as the net force of work

Answer 11

Change in kinetic energy is:

Final kinetic energy - Initial kinetic energy

Question 12

What is gravitational potential energy?

Answer 12

Potential energy is defined as energy that is stored. Objects with potential energy have the ability to apply forces and do work.

In short, GPE is the energy possessed by an object due to its position in the gravitational field

Question 13

What is the formula of gravitational potential energy?

Answer 13

GPE = Mass x Gravity (9.8) x Height

GPE = mgh

Question 14

What is the conservation of energy?

Answer 14

The ‘conservation of energy’ states that energy is neither created nor destroyed. Energy is transferred from one form to another, whether it be from potential to kinetic or vice versa. This means that the mechanical energy is constant and therefore the same, before and after something has happened.

Question 15

Define mechanical energy

Answer 15

Mechanical energy is defined as the energy associated with the position and motion of an object

Em (Initial) = Em (Final)

Question 16

What is power?

Answer 16

Power is the measure of the rate at which work is done.

It is also known as the rate at which energy is transferred.

In short, power is the rate at which work is done or when energy is transferred

Question 17

What is the formula for power?

Answer 17

The formula for power is: (note that ‘p’ is momentum and ‘P’ is Power)

Power = Work / Change in time

P = W/ t (triangle t meaning change in time)

It can also be found by:

Power = Force x Velocity

P = Fv

NOT P=MV
as P is MOMENTUM

Question 18

What does the area underneath a force-distance time graph tell you?

Answer 18

It tells us the work done, since work is equivalent to force applied multiplied by the displacement

Question 19

For the force-time graphs where it goes under the x-axis, how do you calculate the work done?

Answer 19

It will be the absolute value of the area, which represents the work done. Therefore, you will be adding the area underneath the x-axis instead of subtracting them as you would is displacement-time graphs and such

Question 20

If there are multiple bodies in a system, then the work done will be different depending on how you look at it. For example, the amount of work done by the whole system can be zero, but the work done by individual components within that system can be different values other than zero.

True or False?

Answer 20

True