Science Chapter 4 - Lesson 1

Lifting a stone block 146 m to the top of the Great Pyramid required 146,000 J (joules) of work. How much work was done to lift the block halfway to the top?

73,000 J (check homework answer)

Explain why a motionless weight lifter is NOT doing work?

Because the weights are NOT moving, no transfer of energy.

What are 2 ways power can increase?

Do MORE work in same time OR Do the same work in LESS time

Pushing very hard on a heavy dresser that does not move Was work done? In which direction was work done? How did the action change the energy of the object?

No (object didn't move) None No change

What is the power equation?

P=W/t Power measured in watts Work measured in joules (force x distance) Time measured in seconds

How are work and power related?

Power is the rate at which energy is transferred to an object.

True or False: One joule per second equals one watt.

True

How are work and energy related?

Work is the transfer of energy

What is work?

Work is the transfer of energy to an object by a force that makes an object move in the direction of the force; Note: Work is ONLY being done while the force is applied to the object.

Lifting your book from the bottom of your locker: Was work done? In which direction was work done? How did the action change the energy of the object?

Yes Up It increased the potential and kinetic energy as it was lifted.

Pushing a shopping cart through a grocery store Was work done? In which direction was work done? How did the action change the energy of the object?

Yes (object moved) Forward Increased the energy (kinetic to potential)

The work done on an object depends on the ______ of the force and the direction of the __________.

direction motion

Doing work on an object transfers _______ to the object.

energy

An object lifted from the ground _________________ potential energy.

gravitational

All moving objects have ________ energy.

kinetic

As an object's height above the ground increases, its __________ energy increases.

potential

Doing more work quickly affects ___________.

power

What is power?

the rate at which work is done or energy is transferred

The work done to lift any object is equal to the __________ of the object multiplied by the ___________ it is lifted.

weight distance

How is work calculated?

work = force x distance Work - measured in joules Force - measured in newtons Distance - measured in meters