Problems 11-15 Solutions Outline
Problem 11
If you walk
5.0 m horizontally forward at a constant velocity carrying a 10-N object,
the amount of work you do is
A) more than 50 J.
B) equal to 50 J.
C) less than 50 J, but more than 0 J.
D) zero.
A container of water is lifted vertically 3.0 m then
returned to its original position.
If the total weight is 30 N, how much work was done?
A) 45 J
B) 90 J
C) 180 J
D) No work was done.
Problem 13
Does the centripetal force acting on an object do work
on the object?
A) Yes, since a force acts and the object moves, and
work is force times distance.
B) Yes, since it takes energy to turn an object.
C) No, because the object has constant speed.
D) No, because the force and the displacement of the
object are perpendicular.
Problem 14
You throw a ball straight up.
Compare the sign of the work done by gravity while the ball goes up
with the sign of the work done by gravity while it goes down.
A) Work is + on the way up and + on the way down.
B) Work is + on the way up and - on the way down.
C) Work is - on the way up and + on the way down.
D) Work is - on the way up and - on the way down.
Problem 15
The area under the curve, on a Force versus position
(F vs. x) graph, represents
A) work.
B) kinetic energy.
C) power.
D) potential energy.