physics
posted by Anil on .
A partical is projected vertically upward with speed 20 m/s. What will be the time after particle is at a height 15m above the ground( g=15 m/s*s)

h=ho+vi*t1/2 g t^2
15=0+20t4.9t^2
Put it in the form of a quadratic equation
at^2+bt+c=0 and use the quadratic equation. 
If velocity v of particle moving in straight line is related with distance travelled S as v=2(1+S)^1/2. Find the acceleration of the particle.

The actual value of g on Earth is 9.8 m/s^2, which is what BobPursley assumed.
I have no idea you were asked to assume g = 15 m/s^2.
Your followup question should have been posted separately.
Use a = dV/dt = dV/ds * ds/dt = V* dV/ds