Work & Power

The equation for work is

• work = power x mass

• work = power / time

• work = force x distance

• work = distance x time

The equation for POWER is

• power = mass x time

• power = work / time

• power = time / work

• power = work x time

In which of these cases is work being done? 

• A student sleeps all night.
• A student pushes a locked door that does not move.
• A student carries his chair into another room.
• A student sits on the carpet.

A roller coaster whose average speed is 32 m/s is at the top of a 72m hill and weighs 966N. At the top of the hill the coaster car has ___________________ energy.

• only kinetic energy

• only potential energy

• mostly kinetic energy

• both kinetic and potential energy

Which statement does not illustrate power?

• A farmer plowing the rice field all day.

• A Siberian husky pulling a sled all day.

• A principal sitting on a chair while observing several classes all day.

• A teacher encoding his power point presentation in his laptop all day.

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

Which statement illustrates work done?

• A weightlifter holds a barbell above her head.

• A teacher applies a force to a wall and becomes exhausted.

• A rolling marble hits a note card and moves it across a table.

• A waiter carries a tray full of meals across a dining room at a constant speed.

A weightlifter holds a 100 kg barbell above her head. Is work done?

• Yes because there is a force applied to the barbell and the force causes a displacement of the barbell.

• Yes because there is an upward force applied to the barbell and the barbell moves vertically.

• No because no displacement occurred.

• No because there is no force applied.

What is the energy possessed by the cart?

• potential energy

• kinetic energy

• mostly potential

• mostly kinetic

How will you describe the energy at Point C?

• mostly potential energy

• mostly kinetic energy

• losing PE, gaining KE

• losing KE, gaining PE