Concept explainers
Animal Athletes
Different animals have very different capacities for running. A horse can maintain a top speed of 20 m/s for a long distance but has a maximum acceleration of only 6.0 m/s2, half what a good human sprinter can achieve with a block to push against. Greyhounds, dogs especially bred for feats of running, have a top speed of 17 m /s, but their acceleration is much greater than that of the horse. Greyhounds are particularly adept at turning corners at a run.
Figure 1.1
A human sprinter of mass 70 kg starts a run at the maximum possible acceleration, pushing backward against a block set in the track What is the force of his foot on the block?
A. 1500N
B. 840 N
C. 690 N
D. 420N
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