Work, Power & Energy

In which of the following scenarios is work being done, according to the physics definition?

• Solving an equation

• lifting up a book

• holding a barbell above your head

• keeping a bike from falling as it rolls along a sidewalk

The "power" of a machine measures...

• The work it does

• The force it produces

• The rate of doing work

• Its strength

An object lifted 10m gains 200 J of potential energy. If the same object is lifted 20m, its potential energy gain is...

• Half as much

• The same

• Twice as much

• Four times as much

• More than 4 times as much

It takes 60 J of work to push a large box 6 m across a floor. Assuming the push is in the same direction as the displacement, what is the magnitude of the force on the box?

• 6 N

• 10 N

• 60 N

• 360 N

• None of these

A shopping cart has a mass of 40 kg is pushed 10 m with a force of 20 N. How much work is done on the cart?

• 200 J

• 400 J

• 800 J

• 8000 J

How can you increase the power output of a machine?

• Increase the work done

• Increase the force with which the work is done

• Decrease the time in which the work is done

• All of the above

A 10 kg ball has a height of 2 m, while a 5 kg ball has a height of 5 m. Which ball has more potential energy?

• The 5 kg ball

• The 10 kg ball

• They both have the same potential energy

• impossible to predict

How much power is required to raise a 30 kg crate a vertical distance of 6 m in a time of 4 seconds?

• 120 W

• 52.5 W

• 450 W

• 385 W

• 525 W

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

The SI unit of work

• Joules

• Watts

• Newtons

• meters