Answer:
v = 7.4 m/s
Explanation:
Given that,
Mass if a volleyball, m = 5 kg
The ball reaches a height of 2.8 m
We need to find how fast the ball is going as it bumped into the air. Ket the velocity is v. Using the conservation of energy to find it as follows :

So, the required speed is 7.4 m/s. Hence, the correct option is (b).
Answer:
C. She should get the Earth spinning on its axis again.
Explanation:
The Earth experiences day and night because of its spinning on its own axis.
If Kara's science-fiction story doesn't have the Earth spinning on its own axis, then the Earth will not experience day and night and hence Kara should incorporate this idea into his story.
Answer:
1.48kg
Explanation:
Here,
potential energy (P.E) = 29j
height (h) = 2m
acceleration due to gravity(g) =

mass(m) = ?
we know,
P.E = mgh
or, 29 = m×9.8×2
or, 29/19.6 = m
or,m = 1.48kg