Let the key is free falling, therefore from equation of motion
.
Take initial velocity, u=0, so
.

As velocity moves with constant velocity of 3.5 m/s, therefore we can use formula

From above substituting t,
.
Now substituting all the given values and g = 9.8 m/s^2, we get
.
Thus, the distance the boat was from the point of impact when the key was released is 10.60 m.
Mechanical energy is made when something is moved. The energy that is moving is kinetic. And potential energy is stored energy. Mechanical energy can be used to store energy and to cause moving energy. For instance: a slingshot. Pulling back the band creates potential energy and releasing it creates kinetic energy.
P (gravitational force) = m (mass) x g
<=> P = 0.05 x 10
<=> P = 0.5N
I am pretty sure that the only statement which is true for particles of the medium of an earthquake P-wave is being shown in the option : b)vibrate parallel to the wave, forming compressions and rarefactions. As you know, it can be formed in two ways : from alternating compressions and rarefactions or primary wave. I bet you will agree with me.