Stewart – Calculus 8e ET Chapter 6 Form D
____ 17. A force of 30 N is required to maintain a spring stretched from its natural length of 12 cm to a length
of 15 cm. How much work is done in stretching the spring from cm to cm?
a.
b.
c.
d.
e.
____ 18. If J of work are needed to stretch a spring from cm to cm and another J are needed to
stretch it from cm to cm, what is the natural length of the spring? Round the answer to
nearest integer.
a.
b.
c.
d.
e.
____ 19. An aquarium m long, 1 m wide, and 1 m deep is full of water. Find the work needed to pump half
of the water out of the aquarium. (Use the facts that the density of water is )
a.
b.
c.
d.
e.
____ 20. A particle moves a distance of 160 ft along a straight line. As it moves, it is acted upon by a
constant force of magnitude 10 lb in a direction opposite to that of the motion. What is the work
done by the force?
a. –1,600 ft-lb
b.
1
1600
ft-lb
c.
1
16
ft-lb
d.
16
ft-lb