Kinematics rock thrown up in air

AI Thread Summary
A rock thrown upward on Mars with an initial velocity of 22 m/s follows the height equation H = 22t - 1.86t^2. The rock reaches the surface at approximately 11.83 seconds. The velocity at any time t can be calculated using the formula v = 22 - 3.72t. To find the impact velocity, one can use the relationship between initial and final velocities in a conservative field or apply the total time of flight in the kinematic equations. The discussion concludes with a confirmation of the method to calculate the final velocity upon impact.
ankit arya
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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...
 
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Welcome to PF.

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

|Vinitial| = |Vfinal|

... going down.

Or you could do it the long way and evaluate

V = Vinitial - a*t

Using the total time of flight.
 


thanks i got that!
 

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