Work Formal Formative

What is the definition of work we use in Physics?

• force multiplied by time

• Changing the amount of energy an object has

• Applying a force to an object

• Something you do to earn money

A car moving at 30 mph has 140,000 J of energy.

How much work do the brakes need to exert to stop the car

• less than 140,000 J

• 140,000 J

• more the 140,000 J

• brakes are not doing work

A car is moving at 15 mph with 34,000 J of energy. To accelerate 25 mph (94,000 J) How much more energy is needed?

• 34,000 J

• 45,000 J

• 60,000 J

• 128,000 J

The force of friction always takes energy out of a system. It does _________ work

• positive

• negative

• 0

Atlas was a titan (not related to Thanos) in Greek mythology who was condemned to hold the world on his shoulders.

How much work is he doing?

• We need to know how heavy the world is

• We need to know how long he is holding it

• We need to know how strong he is

• He is not doing work because holding an object does not change the energy level of the object

A bobsled team pushes the bobsled team from a stop to 8 mph with 4000J of energy. How much work does the team expend to start the bobsled?

• 1000J

• 2000J

• 4000J

• 8000J

In order to take-off faster some military jets rockets to assist their take off.

These rockets do

• no work just increase the speed of the plane

• do positive work in helping the plane take-off

• do negative work by making the engine job easier

An elevator lifts 1500kg up 8 meters,

• does 120,000 J of work by increasing the potential energy of the elevator car

• can not be determined because we do not know the size of the elevator

• can not be determined because we need to know the time it took.

• does not do work because it is stopped at both the bottom and top.