Conceptual questions
Section 9.1
18. How much work does it take to hold a dumbbell
motionless over your head for 10 s?
19. What physical quantity is measured by a spring scale?
20. String and nylon thread will stretch when pulled with a
moderate force, but only a small amount. If you apply the
same force to a spring and it stretches much further than
the string and thread, how do the spring constants of the
string and thread compare to the spring?
21. How do you account for the mass of the hook when using
a hooked lab mass?
22. Two apartment mates are arguing over the potential energy
of a 10 kg TV that hangs on the wall. The first person
claims that the television is 2 m from the floor so its
potential energy is 10 kg x 9.8 N kg x 2 m = 196 J. The
other claims that since they are on the second floor, the TV
is 12 m above the ground so the potential energy is
10 kg x 9.8 N kg * 12 m =1,176 J. Who is right or are
they both right? Explain.
23. For a classroom investigation, a teacher hangs a heavy
bowling ball by a rope from the ceiling so that the ball
hangs at a height just a little lower than the teacher's nose.
The teacher faces the ball, steps backward a few steps and
draws the ball toward her until it just touches the tip of her
nose. She then asks her class if she will remain uninjured
when she releases the bowling ball-knowing it will
suring away then reverse and string back toward her nose
again How should von answer her?