A 10 kg rock that has been dropped from a 60 meter high cliff experiences a average force of air resistance of 30 N. Calculate the KE at the bottom of the fall.

Explanation:

According to the given situation,

     Change in kinetic energy = work done by all the forces

So,   Change in kinetic energy = work done by gravitational force + work done by air resistance

Initial velocity of the rock will be zero. Since, the gravitational force is in the downwards direction hence, it will be positive. And, force due to air resistance is negative as it is in the upward direction.

Hence, putting the given values into the above formula as follows.

           K.E = 4086 J

Thus, we can conclude that the K.E at the bottom of the fall is 4086 J.          

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min