Work, Energy, and Power

Work and Energy

100

Define: Work

the change in energy of an object done by applying a Force to an object causing it to have displacement

200

What is the formula for work?

W=F(D) D=Distance, meters; F=Force, Newtons

300

When is work done and not done during the lift of a military press?

When the object is being lifted, not at the top when it is still.

400

What is an example of when force is applied by no work is done? 

push on wall or other 

500

1) How much work is done if I pushed a 100 N crate across the floor with a force of 50 N for a distance of 10 M? 2) How much work is done if Ethan pushes a force of 600 against the wall for 30 second?

1) W=F(D) 50N(10M)=500 J 2) NO WORK BECAUSE NOT MOVING

Energy

100

What is an example when an object has gravitational potential energy

Answers Varies

200

A ball falling through the air

gravitational potential energy and kinetic energy

300

A pin ball being pushed into action by a spring. 

mechanical and kinetic (maybe gravitational too!)

400

A hydroelectric dam involves what kinds of energy.

Kinetic, mechanical, electric

500

What is the law of conservation of energy.

Energy is never created, lost, or destroyed. Only transformed.

Work and Power

100

What are the SI units for power?

Watts

200

What is the difference between energy and power?

work and energy don't involve time, but power does

300

What is the formula for power

P=W/T

400

Who does more work? Spencer walking up the 20 m high staircase carrying his backpack in 10 seconds, or John running up the same staircase carrying a backpack in 3 seconds?

Same height, so same work John feels more tired because used more power

500

 runner runs up a flight of stairs using 200J of work in 10 sec

Power: P=W/T= 20 Watts

Work--> Kinetic Energy

100

What is Kinetic Energy?

Energy of a moving object

200

What is the formula for KE?

KE=1/2MV^2 (Joules)

300

Can KE ever be negative?

No, the velocity is squared-->always positive

400

Where is kinetic energy highest on our rollercoasters?

Towards the bottom when it is going fastest

500

What happens if you double velocity and triple the mass?

Proportional reasoning-KE=1/2MV^2=3M(4V)=12KE

Work & Potential Energy

100

What is potential energy.

Energy when an object is still.

200

Define gravitational potential energy?

Energy of an object placed at a height above a reference level

300

What is the formula for gravitational potential energy?

PE=mgh

400

An object has a mass of 250 kg. It is 20 m above the ground. What is the PE?

49,000J

500

A 45 kg skier starts off from rest at the top of the hill 85 m high. How much PEG does the skier have at the top?

PE=mgh =60Kg(10m/s^2)(10m)