In a bicycle race on a straight road, the leader is 72.0 m from the finish line and continues to travel to the finish line with
a constant speed of 12 m/s. When the leader is 72.0 m from the finish line, the second-place rider is 5.0 m behind him and traveling with a speed of 11.0 m/s when she decides to accelerate, keeping a constant acceleration for the rest of the race. The two riders end up crossing the finish line at exactly the same time.(a) Calculate the value of the second rider?s constant acceleration that allows her to cross the finish line at exactly the same time as the first rider.m/s2(b) What is the speed of the second rider as she crosses the finish line?m/s(c) What is the second rider's average speed over the final 77 m of the race?m/s
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There are some missing data in the text of the problem. I've found them online:
a) coefficient of friction dry steel piston - steel cilinder: 0.3
b) coefficient of friction with oil in between the surfaces: 0.03
Solution:
a) The force F applied by the person (300 N) must be at least equal to the frictional force, given by:
where
is the coefficient of friction, while N is the normal force. So we have:
since we know that F=300 N and
, we can find N, the magnitude of the normal force:
b) The problem is identical to that of the first part; however, this time the coefficienct of friction is
due to the presence of the oil. Therefore, we have:
a) coefficient of friction dry steel piston - steel cilinder: 0.3
b) coefficient of friction with oil in between the surfaces: 0.03
Solution:
a) The force F applied by the person (300 N) must be at least equal to the frictional force, given by:
where
since we know that F=300 N and
b) The problem is identical to that of the first part; however, this time the coefficienct of friction is