A runner moving at a speed of 8.8 m/s rounds a bend with a radius of 25 m. Find

Question

A runner moving at a speed of 8.8 m/s rounds a bend with a radius of 25 m. Find the centripetal acceleration of the runner. Which of the forces listed below supplies the force needed to give this acceleration to the runner? Normal Friction Weight Tension A 3.01-kg rock is released from rest at a height of 20.0 m. Ignore air resistance and determine the kinetic energy at 20.0 m, the gravitational potential energy at 20.0 m, the total mechanical energy at 20.0 m, the gravitational potential energy at 0 m, and the total mechanical energy at 0 m. the kinetic energy at 0 m the speed of the rock just before it strikes the ground.

Explanation / Answer

centripetal acceleration = v^2/ R = 8.8^2/25 =3.0976 m/s^2

friction force   

Q6

KE at 20   

velocity at 20 m = 0

so KE = 0

PE = mgH = 3.01*9.8*20 = 589.96 J

Total mechenical energy at 20 m = KE+PE = 589.96 J

gravitational potential energy at 0 m = mgH = 3.01*9.8*0 = 0 J

KE at 0 m = 589.96 J by energy conservation

Total mechenical energy at 0 m = KE+PE = 589.96 J ( by energy conservation )

speed of block

v^2 = u^2 +2*a*s

v^2 = 0+ 2*9.8*20

v = 19.799

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