Chapter 9: Q. 4 (page 227)
The rope in FIGURE Q9.4 pulls the box to the left across a rough surface. Is the
work done by tension positive, negative, or zero? Explain.
Work done is positive .
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The human heart pumps the average adult’s of blood through the body every minute. The heart must do work to overcome frictional forces that resist blood flow. The average adult blood pressure is
a. How much work does the heart do to move the of blood completely through the body?
b. What power output must the heart have to do this task once a minute?
Hint: When the heart contracts, it applies force to the blood. Pressure is Model the circulatory system as a single closed tube, with cross-section area and volume filled with blood to which the heart applies a force.
FIGURE is the force-versus-position graph for a particle moving along the axis. Determine the work done on the particle during each of the three intervals m, m, and m.
At what speed does a 1000 kg compact car have the same kinetic energy as a 20,000 kg truck going 25 km/h?
A horizontal spring with spring constant N/m extends outward from a wall just above floor level. A kg box sliding across a frictionless floor hits the end of the spring and compresses it cm before the spring expands and shoots the box back out. How fast was the box going when it hit the spring?
A pile driver lifts a weight and then lets it fall onto the end of a steel pipe that needs to be driven into the ground. A fall of drives the pipe in . What is the average force exerted on the pipe?
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