physics problems....help!!?

Question

a block of mass 0.5 kg is pushed against a horizontal spring of negligible mass, compressing the spring a distance of delta x. the spring constant is 418 N/m. when released, the block travels along a prictionless, horizontal surface to point B, the bottom of a vertical circular track of radius 0.4 m, and continues to move up the track. the speed of the block at the bottom of the track is 14 m/s and the block experiences an average frictional force of 6 N while sliding up the track. the acceleration of gravity is 9.8 m/s^2

a) what is delta x?? in units of m

b) what is the speed of the block at the top of the track? in units of m/s

c) what is the centripetal acceleration of the block at the top of the track? in units of m/s^2

Answer 1

a)
(1/2)(418)(∆x)^2 = (1/2)(0.5)14^2
(∆x)^2 = 0.5*196/418
∆x = 234 mm

b)
(1/2)(0.5)v^2 = (1/2)(0.5)14^2 - 0.5(9.8)(0.8) - 6(0.4)π
v^2 = 4(49 - 3.92 - 7.5398)
v^2 = 37.540 m^2/s^2
v = 6.1270 m/s

c)
a = v^2/r = (37.540 m^2/s^2)/(0.4 m)
a = 93.850 m/s^2 supplied by the track
Gravitational acceleration is not included.

Answer 2

why 196