I think it is -3.99 x 102 j
Answer:
Explanation:
Given
Initial speed is u=V
Maximum height of Pebble is H
Deriving maximum height of Pebble and considering motion in vertical direction

where v=final velocity
u=initial velocity
a=acceleration
s=Displacement
Final velocity will be zero at maximum height


i.e. maximum height is dependent on square of initial velocity
for twice the height

on comparing
Answer:
Depends.
Explanation:
Whether the object is going left or right, the speed will stay the same until friction eventually stops it. <em>However, </em>if, for example, we're talking about an object going straight before veering right, then yes, speed <em>does</em> matter. An object will normally have to speed up or slow down momentarily when changing direction to keep itself sustained on the ground.
So, honestly? It really depends on what we're talking about!
Hope this helped!
Source(s) used: None.