Work Done on an Object

OPENING PRAYER

WORK

• quantity that exists whenever a force acting upon an object causes a displacement.

• scalar quantity

Remember:

Work is positive when angle is greater than 0 degree and less than 90 degrees.

Work is negative when angle is greater than 90 degrees and not greater than 180 degrees.

Two Important Conditions in the Definition of Work

• The force must move the object.

• The force must have a component parallel to the direction of motion.

Situational Analysis

Multiple Choice

Which of the following situations shows that work is done?

• teacher sitting on a chair

• book resting on a table

• key chain hanging from a bag

• a ball being rolled on the floor

Multiple Choice

In which of the following situations is work NOT done?

• pushing a cart in a store

• shooting a basketball

• holding a 20 pound box above the floor

• running a mile

Multiple Choice

In which of this cases is work being done?

• a student sleeping

• a student pushing a locked door

• a student carrying his chair into another room

• a student sitting on the carpet

Multiple Choice

True or False: You do work when you mannequin pose with an object in your hand.

• True

• False

APPLICATION

Multiple Choice

If you push a cart with a force of 60 N for 2 m. How much work have you done?

• 120 J

• 30 J

• 120 N

• 30 N

Multiple Choice

It took 500 Newtons of force to push a car 4 meters. How much work was done?

• 2000 J

• 125 J

• 0.008 J

• 500 J

Multiple Choice

If 68 Joules were necessary to move a 4 Newton crate, how far was the crate moved?

• 272 m

• 17 m

• 4.05 m

• 272 cm

Multiple Choice

Two people push on a wall with 100 N. The wall doesn’t move. How much work is done?

• 100 J

• 100 N

• 0 J

• 0 N

Multiple Choice

Andrew who weighs 80 kg, uses 180 N of force to get him up the slope. The vertical distance is 2 m and the diagonal is 10 m. Calculate the work he does.

• 160 J

• 1,600 J

• 1,800 J

• 3,600 J