We have
. So,
.
. So
.
Thus we can convert the units of the given quantity.
That is,
.
The quantity is converted to the required units.
b is the answer i hope this helped...
The position of the first ball is

while the position of the second ball, thrown with initial velocity
, is

The time it takes for the first ball to reach the halfway point satisfies



We want the second ball to reach the same height at the same time, so that




More force is needed for more mass. Therefore, if the mass is greater and the force is not enough then the object will less likely accelerate