It’s either movement or work or that’s what a quizzie said
To determine the speed relative to the ground, since the ground is our reference frame, it would be v = 0, for the kid on the skateboard, you would need to take into account the speed that he/she is going and the speed of the keys thrown at.
I believe.
41.2 = h-1/2g(t-1)^2
<span> {-h = -1/2gt^2-1/2g+g*t-41.2
</span><span> {h = 1/2gt^2
</span><span> summing them up
</span><span> 0 = -1/2g+g*t-41.2
</span><span> 41.2 +4.9 = g*t
</span><span> t = 46.1/9.8 = 4.70 sec
</span><span> h = 1/2gt^2 =4.9*(4.70^2) = 108.241 m </span>
