A particle, moving in a straight line, passes through a fixed-point O.Its velocity vms-1, t seconds after passing through O, is given by v = k cos 4t, where k is a positive constant.
a. Find the value of t when the particle is first instantaneously at rest.
b. Find an expression for the acceleration, a, of the particle t seconds after passing through .
c. Given that the acceleration of the particle is 10 ms-2 when t = 7π/24, find the value of k