Arock is dropped from rest from a height h above the ground. it falls and hits the ground with a
speed of 11 m/s. from what height should the rock be dropped so that its speed on hitting the ground
is 22 m/s? neglect air resistance

Use energy conservation, since no energy is lost it must be constant.

E = 0.5mv² + mgh

At release the velocity v = 0 and the height is h.

E = 0 + mgh

At impact the height h = 0 and the velocity is v.

E = 0.5mv² + 0

Since the energy E is conserved:

0.5mv² = mgh

the mass m cancels and the equation becomes:

0.5v² = gh

h = 0.5v²/g

when g = 9.81 and v = 22:

h = 24,66

The best answer is (a) which is universal law is in effect at all times. it is constantly at play in everything we do and governs our lives. it is also important to note that universal law applies to not only everything on earth, but everything in the universe as well, which is another reason why it is in effect at all times.

35.98  million  mile my friend