Negative work can be done
a. by friction on the tires while a car is accelerating without skidding.
b. by a spring at the bottom of an elevator shaft when it stops a falling elevator.
c. by a hand catching a ball.
d. by all of the above. e. only by (b) and (c) above.
E
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A car traveling along the highway brakes to a stop over a certain distance. More braking force is required if the car has
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Indicate whether the statement is true or false
A uniform ladder 15 ft long is leaning against a frictionless wall at an angle of 53° above the horizontal. The weight of the ladder is 30 pounds. A 75-lb boy climbs 6.0-ft up the ladder. What is the magnitude of the friction force exerted on the ladder by the floor?
a. 43 lb b. 34 lb c. 38 lb d. 47 lb e. 24 lb