here is a link to the same question so you can see what the diagram looks like:

Question

here is a link to the same question so you can see what the diagram looks like:

http://www.chegg.com/homework-help/questions-and-answers/figure-small-block-mass-m-0036-kg-slide-thefrictionless-loop-loop-loop-radius-16-cm-block--q358860

Here are my numbers:

In the figure, a small block of mass m = 0.049 kg can slide along the frictionless loop-the-loop, with loop radius R= 15 cm. The block is released from rest at point P, at height h = 5R above the bottom of the loop. What are the magnitudes of (a) the horizontal component and (b) the vertical component of the net force acting on the block at point Q? (c) At what height h should the block be released from rest so that it is on the verge of losing contact with the track at the top of the loop? (On the verge of losing contact means that the normal force on the block from the track has just then become zero).

Explanation / Answer

a) m = 0.049 kg
R = 0.15 m

h = 5*R = 0.75 m


m*g*h = 0.5*m*v^2 + m*g*R

0.5*m*v^2 = m*g*(5R-R)

v = 3.43 m/s

a) Fx = m*v^2/R = 3.842 N

b) Fy = m*g = 0.049*9.8 = 0.4802 N


c)
let H is the hight needed

at top point of the loop, h = 2*R

m*v^2/R = g

v = sqrt(g*R) ( minimum speed)

at top point of the loop,

m*g*H = 0.5*m*v^2 + m*g*2*R

m*g*H = 0.5*m*g*R + 2*m*g*R

H = (0.5*R+2*R)

H = 0.375 m

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