A popular circus act features daredevil motorcycle riders encased in the \"Globe

Question

A popular circus act features daredevil motorcycle riders encased in the "Globe of Death" (see the figure below), a spherical metal cage of diameter 17 ft. Assume a speed of 23 mi/h for both tricks.

A) A rider of mass 69 kg on a 125-cc (95-kg) motorcycle keeps his bike horizontal as he rides around the "equator" of the globe. What coefficient of friction is needed between his tire and the cage to keep him in place?

B)How many loops will the rider make per second?

C)The same rider performs vertical loops in the globe. What force does the cage need to withstand at the top and the bottom of the rider's loop?

--Ftop?

--Fbottom?

Explanation / Answer

A) for biker to be in horizontal position

friction force = mg

(mu)N = mg and N = cenrigugal force = mv^2/r

(mu)mv^2/r = mg

(mu) = gr/v^2 = 9.8 x 2.6 /(10.28^2) = 0.24

coefficient of friction = 0.24

B) v = wr

w = 3.95 rad/s

0.62 revolution per second

C)Ftop = mv^2/r - mg = 5058.66 N

Fbottom = mv^2/r + mg= 8273.06 N

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