Work, Energy, & Power Review

Work, Energy, & Power Review

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Work

Work is the transfer of energy that results in an object's movement.

- W = Fd or W = Fdcos(θ)

- F is the force applied

- d is the distance traveled

- θ is the angle the force makes with the distance traveled.

Multiple Choice

How do we calculate work?

• W = F * d

• w = f * D

• W = F * D

• w = f * d

Multiple Choice

How much work is being done with 200 N of force over 426 meters?

• 85,200 J
• 45,620 J
• 90,480 J
• 62,329 J

Multiple Choice

50 J of work is done lifting a 2.0 kg book in the air. How high was it lifted?

• 2.6 m

• 3.6 m

• 1.0 m

• 25 m

Fill in the Blank

If you exert a 10 N force to lift a box 5 m, how many Joules of work do you do?

(Number only)

Energy

• Energy is often defined as the ability to do work

• It is measured in Joules

• Kinetic Energy (KE) = (1/2)mv²

• Potential Energy (GPE) = mgh

• Remember! g = 9.81 m/s²

Multiple Choice

What is the potential energy of a 3kg ball that is on the ground?

• 0 J

• 3 J

• 9.8 J

• 29.4 J

Multiple Choice

A 3.0 kg ball is on a table 1.5 m above the ground. What is its gravitational potential energy?

• 4.5 J

• 44.1 J

• 3.4 J

• 29.4 J

Multiple Choice

What is the kinetic energy of a 12 kg dog running at 3 m/s?

• 36 J

• 353 J

• 54 J

• 118 J

Power

• Power is the rate of work done

• P = W / t

• Power is measured in Watts (W)

• 1 Watt = 1 Joule/second

• 1 horsepower (HP) = 745.7 watts

Multiple Choice

How do you calculate power?

• P = W / t

• P = E / t

• P = w * t

• P = t / W

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

Fill in the Blank

If you exert 500 N to climb 5 m up a flight of steps in 10 seconds, how many watts of power did you exert?

(number only)

Multiple Choice

How much energy is used by a 100 W light bulb over 1 hour? (be sure to convert to seconds first)

• 100 J

• 36,000 J

• 360,000 J

• 240,000 J