Work and Power

Work and Power

​Some text here about the topic of discussion.

Energy Review

Remember that mechanical energy is conserved

Total energy = potential energy + kinetic energy

Some text here about the topic of discussion

Multiple Choice

What is the total mechanical energy for the position of the ball indicated by the blue circle?

• 0 J

• 50 J

• 100 J

Multiple Choice

What is the total mechanical energy that the ball would have when it is in the position indicated by the blue circle?

• 0 J

• 50 J

• 100 J

Multiple Choice

How much kinetic energy would the ball have at the position indicated by the blue circle?

• 0 J

• 50 J

• 100 J

Multiple Choice

If the ball has a mass of 4kg, what would be the velocity of the ball at the position indicated by the blue circle?

$$KE\ =\ \frac{1}{2}mv^2$$

• 0 m/s

• 5 m/s

• 25 m/s

Both are measured in JOULES

Energy is the ability to do work and work causes a change in energy

​ex. If you do 30 J of work on an object, its energy will change by 30 J

Work - how much the position of an object is changed by a force

​Some text here about the topic of discussion.

In order to do work, the object must MOVE in the same direction as the force

Multiple Choice

Your car is stuck in the mud. You push with 500 N of force but it never moves. How much work did you do?

• 0 J

• 500 J

• 500 N

• 0 N

Match

Match the variables with the correct answer.

W = F x d

• F = 20 N

  d = 5 m

• W = 15 J

  d = 5 m

• W = 20 J

  F = 2 N

• F = 8 N

  d = 4 m

100 J

3 N

10 m

32 J

• 100 J

• 3 N

• 10 m

• 32 J

Power is the rate at which work is done

AKA - The change in energy over time

The faster the work is done, the more power

The equations for work and power can be combined to simplify problem solving.

​Since W = Fd and P = W/t,

We can say that P = Fd/t

Multiple Choice

You do 90 joules of work in 30 seconds. How much power have you generated?

• 30 watts

• 3 watts

• 120 watts

• 270 watts

Multiple Choice

If 68 W of power is produced in 18 seconds, how much work is done?

• 1,224 J

• 0.264 J

• 3.77 J

• 12.24 J

Multiple Choice

How much time is needed to produce 720 Joules of work if 90 watts of power is used? 

• 0.125 s

• 8 s

• 64800 s

• 80 s

Multiple Choice

A 100 N force is applied to move an object a horizontal distance of 5 meters at constant speed in 10 seconds. How much power is done?

• 50J

• 50W

• 500J

• 500W