physics projectile motion

Question

An astronaut on a distant planet wants to determine its acceleration due to gravity. The astronaut throws a rock straight up with a velocity of 14.1m/s and measures a time of 12.0s before the rock returns to his hand. What is the acceleration due to gravity in m/s2 on this planet?

Answer 1

a = acceleration of gravity on the planet (a positive number)

 

h(t) = -at²/2 + v₀t 

 

v₀ = 14.1 m/s

 

h(t) = -at²/2 + 14.1t

 

At 12.0 s, h = 0.  Set h(12.0) = 0 and solve for a.

 

0 = -a(12.0)²/2 + 14.1(12.0)

 

Now solve for a and finish from here.  The result will be in m/s².