Kinematics rock thrown up in air

[ankit arya]

kinematics ... rock thrown up in air

Homework Statement

If a rock is thrown upward on the planet Mars with a velocity of 22 m/s, its height (in meters) after t seconds is given by H = 22t - 1.86t^2.
Find the velocity of the rock when t = a.
When will the rock hit the surface?
With what velocity will the rock hit the surface?

Homework Equations

v=u+at

The Attempt at a Solution

i found the ans for first two ques but i am not able to solve the third one.

velocity at t=a is 22-3.72a
rock will hit the surface at t=11.83s

pls help me with the third one...

 

[LowlyPion]

Welcome to PF.

Gravity is a conservative field. So at the same height going up ...

|V_initial| = |V_final|

... going down.

Or you could do it the long way and evaluate

V = V_initial - a*t

Using the total time of flight.

 

[ankit arya]

thanks i got that!