Work, Power, and Energy

A boy does 18 J of work in 2 s on his backpack as he lifts it from a table.

How much power did the boy use on the backpack?

( Include your units!)

Answer explanation

Power is calculated as work done divided by time. Here, power = 18 J / 2 s = 9 W. Therefore, the boy used 9 watts of power on the backpack.

You do work when you mannequin pose with an object in your hand.

• True

• False

Answer explanation

The statement is false because posing with an object does not involve physical effort or energy transfer, which are necessary for work in a physics context.

Work divided by time equals...

• energy

• power

Answer explanation

Work divided by time gives us power, which measures the rate at which work is done. Therefore, the correct answer is power.

The unit used to measure power is the 

• Watt

• Newton

• Joule

• Newton*meter

Answer explanation

The unit used to measure power is the Watt. It quantifies the rate of energy transfer, while Newton measures force, Joule measures energy, and Newton*meter measures torque.

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

Answer explanation

To find the time, use the formula: time = work / power. Here, time = 720 J / 90 W = 8 s. Thus, the correct answer is 8 s.

Two factors that determine work are...

• Force

• Mass

• Velocity

• Distance

Answer explanation

Work is determined by two factors: the force applied and the distance over which it is applied. Therefore, the correct answers are Distance and Force.

True or false
You do work only when you exert a force on an object and move it

• true

• false

Answer explanation

True. Work is defined as the product of force and displacement. You only do work when you exert a force on an object and cause it to move in the direction of that force.

work is a measurement of how much force is applied over a certain

• distance

• velocity

• shape

• size

Answer explanation

Work is defined as the product of force applied over a distance. Therefore, the correct answer is 'distance', as it directly relates to how work is calculated in physics.

units for work are

• netwons

• joules

• meters

• seconds

Answer explanation

The unit of work in physics is measured in joules. Joules quantify energy transfer when a force is applied over a distance, making it the correct choice. Newtons measure force, while meters and seconds are units of distance and time, respectively.

Tags

NGSS.MS-PS3-5

work transfers

• sweat

• energy

• velocity

• effort

Answer explanation

Work transfers energy, which is the capacity to do work. While effort and sweat may relate to physical activity, they do not define the concept of work in physics, making energy the correct choice.

Tags

NGSS.MS-PS3-5