Two rock climbers, Bill and Karen, use safety ropes of similar length. Karen’s rope is more elastic, called a dynamic rope by climbers. Bill has a static rope , not recommended for safety purposes in pro climbing. ( a ) Karen falls freely about 2.0 m and then the rope stops her over a distance of 1.0 m (Fig. 4–60). Estimate how large a force (assume constant) she will feel from the rope. (Express the result in multiples of her weight.) ( b ) In a similar fall, Bill’s rope stretches by only 30 cm. How many times his weight will the rope pull on him? Which climber is more likely to be hurt? FIGURE 4–60 Problem 82.
Two rock climbers, Bill and Karen, use safety ropes of similar length. Karen’s rope is more elastic, called a dynamic rope by climbers. Bill has a static rope , not recommended for safety purposes in pro climbing. ( a ) Karen falls freely about 2.0 m and then the rope stops her over a distance of 1.0 m (Fig. 4–60). Estimate how large a force (assume constant) she will feel from the rope. (Express the result in multiples of her weight.) ( b ) In a similar fall, Bill’s rope stretches by only 30 cm. How many times his weight will the rope pull on him? Which climber is more likely to be hurt? FIGURE 4–60 Problem 82.
Two rock climbers, Bill and Karen, use safety ropes of similar length. Karen’s rope is more elastic, called a dynamic rope by climbers. Bill has a static rope, not recommended for safety purposes in pro climbing. (a) Karen falls freely about 2.0 m and then the rope stops her over a distance of 1.0 m (Fig. 4–60). Estimate how large a force (assume constant) she will feel from the rope. (Express the result in multiples of her weight.) (b) In a similar fall, Bill’s rope stretches by only 30 cm. How many times his weight will the rope pull on him? Which climber is more likely to be hurt?
Two rock climbers, Jim and Karen, use safety ropes of simi-
lar length. Karen's rope is more elastic, called a dynamic
rope by climbers. Jim has a static rope, not recommended
for safety purposes in pro climbing. (a) Karen (Fig. 4–71)
falls freely about 2.0 m and then the rope stops her over a
distance of 1.0 m. Estimate how large a force (assume
constant) she will feel from the rope. (Express the result
in multiples of her weight.) (b) In a similar fall, Jim's rope
stretches by only 30 cm. How many times his weight will
the rope pull on him? Which climber is more likely to
be hurt?
FIGURE 4–71
Problem 85.
As shown in Fig. 4–70, five balls (masses 2.00, 2.05, 2.10,
2.15, 2.20 kg) hang from a crossbar. Each mass is sup-
ported by "5-lb test" fishing line which will break when
its tension force exceeds 22.2 N (= 5.00 lb). When this
device is placed in an elevator, which accelerates upward,
only the lines attached to the 2.05 and 2.00 kg masses do
not break. Within what range is the elevator's acceleration?
2.20 2.15 2.10 .05 2.00 kg|
FIGURE 4-70
Problem 84.
A 72-kg water skier is being accelerated by a ski boat on
a flat (“glassy") lake. The coefficient of kinetic friction
between the skier's skis and the water surface is Mk = 0.25
(Fig. 4–74). (a) What is the skier's acceleration if the rope
pulling the skier behind the boat applies a horizontal ten-
sion force of magnitude FT = 240 N to the skier (0 = 0°)?
(b) What is the skier's horizontal acceleration if the rope
pulling the skier exerts a force of FT = 240 N on the
skier at an upward angle 0 = 12°? (c) Explain why the
skier's acceleration in part (b) is greater than that in
part (a).
FT = 240 N
Mk = 0.25
FIGURE 4-74 Problem 91.
Chapter 4 Solutions
Physics for Scientists and Engineers with Modern Physics
College Physics: A Strategic Approach (3rd Edition)
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