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Vocab
Work & Power
Energy
Calculating Work, Power & Energy
Potpourri
100
the product of force and distance
What is work?
100

What does work require?

Force and displacement to be parallel.

100

A 7 kg object is motionless.  Calculate kinetic energy.

0 J
100

A 500 kg roller coaster is traveling 7 m/s at a height of 25 m.  Calculate mechanical energy.

134750 J

100

A 2,500 kg race car accelerates from rest to 35 m/s in 7.3 s.  What is the power output of the engine?

209,760 W or 210 kW

200

Energy stored based on height

What is gravitational potential energy?

200

Work is positive when...

The force and displacement are in the same direction.

200

True or False:  Work is equal to a change in kinetic energy if there is no change in height.

True

200

A 2.1 kg rock is being held at a height of 8.7 m.  Calculate it's kinetic energy just before hitting the ground.

179 J
200

Kyle is pushing his physics book away from him across the table. Is work being done?

Yes

300

Stored energy is known as

What is potential energy?

300
True or False? Any part of a force that does not act parallel to the direction of motion does no work on an object.
True.
300
The sum of kinetic and potential energy.

What is mechanical energy?

300

A spring with a spring constant of 125 N/m is stretched to 1.7 m. Calculate its elastic potential energy if its rest position is 1.3 m.

10 J

300

A 1500 kg car is being pushed down a road at a speed of 1.4 m/s.  How much work must be done to increase the speed to 1.9 m/s

1237.5 J

400
rate of doing work
what is power?
400

True or False. (Assume masses are equal.) You and me both lug our books up a flight of steps. You get up there in 1 minute while it takes me 1.5 minutes. I am more powerful than you.

False

400

Energy of motion

What is kinetic energy?

400
Erin is lifting a 7 kg bowling ball up from the 2nd floor to the third from over the railing a distance of 2.5 meters. What is the work done?
171.5 Joules
400

Peter is setting a box down on the floor.  Is work being done?

Yes, negative work.

500

A unit of power which equals to one joule per second

The Watt?

500
If the force applied to an object that is moved is quadrupled but moved for half the original distance, what happens to the work done?
Twice the Work
500

A 2.9 kg object has 656 J of kinetic energy. Calculate velocity.

21.3 m/s

500
Your family is moving to a new apartment. While lifting a box 1.5 m straight up to put it on a truck, you exert an upward force of 200 N for 1.0 s. How much power is requried to do this?
Force is 200 N Formula : Power=work/power Time is 1.0 s = Force X Distance/ Time Distance is 1.5 m Power=200 N X 1.5 m/1.0 s = 300J/s= 300 W Formula: Power= work/time
500

Steph is carrying her book across the room by balancing the book steady on her hand. Is work being done?

No