Answer:
C) one-half as great
Explanation:
We can calculate the acceleration of gravity in that planet, using the following kinematic equation:

In this case, the sphere starts from rest, so
. Replacing the given values and solving for g':

The acceleration due to gravity near Earth's surface is
. So, the acceleration due to gravity near the surface of the planet is approximately one-half of the acceleration due to gravity near Earth's surface.
Because it's the planet in our solar system with the shortest,
fastest orbit around the sun ... only 88 Earth days.
The people who named it didn't know that ... they still thought that
the sun and all the planets revolve around the Earth. But they did
see it zip from one side of the sun to the other, faster than any other
planet ... the result of having the shortest, fastest orbit of any planet.
Answer:
u = - 38.85 m/s^-1
Explanation:
given data:
acceleration = 2.10*10^4 m/s^2
time = 1.85*10^{-3} s
final velocity = 0 m/s
from equation of motion we have following relation
v = u +at
0 = u + 2.10*10^4 *1.85*10^{-3}
0 = u + (21 *1.85)
0 = u + 38.85
u = - 38.85 m/s^-1
negative sign indicate that the ball bounce in opposite directon