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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 are parallel.

force acting upon an object and the object's movement to be in the same direction.

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

this type of thermal energy transfer that causes a metal pan to heat up when it is placed on a stove.

conduction

200

The energy of motion is called ...

kinetic 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.

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

Transfer of thermal energy when warm fluids rise, and cool fluids sink, creating a current.

convection

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

You are riding in a roller coaster going up a hill, at the top your car stops briefly before you start racing down to the bottom of the hill. At which point (stopped at the top or stopped at the bottom of the hill) do you have the most potential energy? Explain your answer..

stopped at top of hill because it has higher height (GPE = ham)

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

This type of thermal energy transfer is why you feel warmth from the sun.

radiation


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

  1. You are riding in a roller coaster going up a hill, at the top your car stops briefly before you start racing down to the bottom of the hill. At which point (stopped at the top or racing towards the bottom of the hill) do you have the most kinetic energy? Explain your answer.

racing towards the bottom of the hill because you are moving

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

Choose the situation in which the person has the most power, then explain why.

  1. Walking 2 miles

  2. Running 2 miles

  3. Crawling 2 miles

Running 2 miles because it takes less time

(P = w / t )

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.

KE = (1/2)m(v^2)

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

What happens when cold milk is poured into hot chocolate?

Energy flows from the _____ to the ______

The kinetic energy of the milk ______

energy flows from the hot chocolate to the milk.

The kinetic energy of the milk Increases.