If it's not falling through air, water, smoke, or anything else,
and gravity is the only force on it, then its speed increases
at a constant rate ... 9.8 meters per second for every second
it falls. (That's the number on Earth. It's different in other places.)
Answer:

Explanation:
As per energy conservation we can say that energy stored in the spring at the position of maximum compression must be equal to the kinetic energy of bullet and block system
so here we have

here we know that
k = 205 N/m
x = 35 cm

now by momentum conservation we know that


now plug in all values in it

now from above equation


by solving above equation we have

I beleve the answer is D).
Explanation:
They will have not much control over their speed or rotational energy. they will carry a lot of gravitation potential energy which will get converted to kinetic energy as they fall through the atmosphere. They will reach their terminal velocity, the fastest they can travel with earth's gravity before they pull their parachute, when they use a parachute to extend their surface area, increasing wind resistance. this allows them to land safely.
Answer:

Explanation:
Given that
Mass of rifle = M
Initial velocity ,u= 0
Mass of bullet = m
velocity of bullet = v
Lets take final speed of the rifle is V
There is no any external force ,that is why linear momentum of the system will be conserve.
Initial linear momentum = Final linear momentum
M x 0 + m x 0 = M x V + m v
0 = M x V + m v

Negative sign indicates that ,the recoil velocity will be opposite to the direction of bullet velocity.