Physic Review of Work

In which of the following sentences is work used in the scientific sense of the word?

• Holding a heavy box

• A scientist works on an experiment in the lab

• Sam and Rachel push hard on a stationary car

• John learned that shoveling snow is hard work

A force does work on an object if a component of the force

• is perpendicular to the displacement of the object.

• is parallel to the displacement of the object.

• perpendicular to the displacement of the object moves the object along a path that returns the object to its starting position.

• parallel to the displacement of the object moves the object along a

  path that returns the object to its starting position.

In which of the following scenarios is no net work done

• A car accelerates down a hill.

• A car travels at a constant speed on a flat road

• A car decelerates on a flat road

• A car decelerates as it travels up the hill

A child moving at constant velocity carries a 2 N ice-cream cone 1 m across a level surface. What is the net work done on the ice-cream

• 0 J

• 2 J

• 3 J

• 1 J

A worker pushes a box with a horizontal force of 50.0 N over a level distance of 5.0 m. If a frictional force of 43 N acts on the box in a direction opposite to that of the worker, what net work is done on the box

• 8.1 J

• 250 J

• 10 J

• 35 J

A worker picks up a heavy box, lifts it to his wast, waits 3 seconds, then places it back down. What is the work the man applies when he is putting it back down?

• 0 J

• The work he applies is positive because he is pulling up on it

• The work he applies is negative because he is applying a force in the opposite direction it is going

• None of the above

A worker picks up a heavy box, lifts it to his wast, waits 3 seconds, then places it back down. What is the work the man applies when he is lifting up the box

• 0 J

• The work the man applies is positive because the work is headed in an upward direction

• The work the man applies is positive because the work is in the same direction as where the box is headed

• The work is negative because it is perpendicular to the box