How much kinetic energy does a 150 N (Newton) barrel have upon striking the ground from a height of 5m?

Question

how fo you solve this? it's really confusing. :l

Answer 1

E(kin)=E(pot)

This means:
E(kin)=m*g*h

Since m*g equals force, the kinetic energy the barrel will have upon hitting the floor is:
E(kin)=5m*150N=750J

Answer 2

The KE = PE solution is the best one.

Note that PE = mgh is just force over a distance, which is by definition work. Here the force is weight (mg = W = 150N) and the distance is the height (h = 5m) of the object above ground.

Unfortunately, physicists live for public recognition; so they have to give proper names (to honor their own) to things rather than leave them in meaningful kg-meter-second units; so they call Newton-meters Joules. I, frankly, would leave PE = mgh in kg (m/sec)^2 units because they are much more useful for further calculations if needed.

Energy, by definition, is the ability to do work or cause a change. So we call PE "potential" because, even though the ability is there, we are not moving...we are not actually realizing work until the body moves.

KE, on the other hand, occurs only when a body is in motion; thus, we call it kinetic. So, KE is realized work because the body of mass m is moving over some distance. We set KE = PE because we are saying the PE is converted to KE when the body is actually dropped from the height h.

As an aside, that PE didn't just happen you know. Something or someone lifted that 150N to 5 meters off the ground in the first place. And that, my friend, took energy to do that work. Discounting efficiency losses...how much work did it take to lift that barrel 5 meters? Was that work KE or PE during the lifting?

Answer 3

a 150N barrel will have a mass of 150/10kg(approx value of gravity=10m/s^2)
mass of barrel = 15kg
by conservation of mechanical energy
therefore potential energy of barrel(P.E) = kinetic energy(K.E)
P.E= mgh
=15x10x5
=750 J

Answer 4

that is if we neglect energy losses due to friction (ie air resistance)

Answer 5

187,500 joules

K= (0.5)mv^2

K= (0.5)150N*50m/s ^2

Answer 6

i don't know