BIO Fish Navigation. (a) As you can tell by watching them in an aquarium, fish are able to remain at any depth in water with no effort. What does this ability tell you about their density? (b) Fish are able to inflate themselves using a sac (called the swim bladder ) located under their spinal column. These sacs can be filled with an oxygen-nitrogen mixture that conies from the blood. If a 2.75-kg fish in freshwater inflates itself and increases its volume by 10%, find the net force that the water exerts on it. (c) What is the net external force on it? Does the fish go up or down when it inflates itself?
BIO Fish Navigation. (a) As you can tell by watching them in an aquarium, fish are able to remain at any depth in water with no effort. What does this ability tell you about their density? (b) Fish are able to inflate themselves using a sac (called the swim bladder ) located under their spinal column. These sacs can be filled with an oxygen-nitrogen mixture that conies from the blood. If a 2.75-kg fish in freshwater inflates itself and increases its volume by 10%, find the net force that the water exerts on it. (c) What is the net external force on it? Does the fish go up or down when it inflates itself?
BIO Fish Navigation. (a) As you can tell by watching them in an aquarium, fish are able to remain at any depth in water with no effort. What does this ability tell you about their density? (b) Fish are able to inflate themselves using a sac (called the swim bladder) located under their spinal column. These sacs can be filled with an oxygen-nitrogen mixture that conies from the blood. If a 2.75-kg fish in freshwater inflates itself and increases its volume by 10%, find the net force that the water exerts on it. (c) What is the net external force on it? Does the fish go up or down when it inflates itself?
4.46
The two blocks in Fig. P4.46 are connected
by a heavy uniform rope with a mass of 4.00 kg. An up-
ward force of 200 N is applied as shown. (a) Draw three
free-body diagrams: one for the 6.00 kg block, one for
B
the 4.00 kg rope, and another one for the 5.00 kg block. For each force,
indicate what object exerts that force. (b) What is the acceleration of the
system? (c) What is the tension at the top of the heavy rope? (d) What is
the tension at the midpoint of the rope?
Figure P4.46
F= 200 N
4.00 kg
6.00 kg
5.00 kg
4.35 ⚫ Two adults and a child want to push a wheeled cart in the direc-
tion marked x in Fig. P4.35 (next page). The two adults push with hori-
zontal forces F and F as shown. (a) Find the magnitude and direction of
the smallest force that the child should exert. Ignore the effects of friction.
(b) If the child exerts the minimum force found in part (a), the cart ac-
celerates at 2.0 m/s² in the +x-direction. What is the weight of the cart?
Figure P4.35
F₁ = 100 N
60°
30°
F2 = 140 N
4.21 ⚫ BIO World-class sprinters can accelerate out of the starting
blocks with an acceleration that is nearly horizontal and has magnitude
15 m/s². How much horizontal force must a 55 kg sprinter exert on the
starting blocks to produce this acceleration? Which object exerts the
force that propels the sprinter: the blocks or the sprinter herself?
Human Physiology: An Integrated Approach (8th Edition)
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