(a) How much work is done in raising a 50 kg crate a distance of 1.5 m above a store room floor?

Question

(b) What is the change of potential energy as a result of this move? (c) How much kinetic energy will the crate have as it falls and hits the floor?

Answer 1

(a) W=mgh = 50*9.8*1.5 = 735 J
(b) delta Ep = 735 J
(c) Ek = 735 J

Doug

Answer 2

a) You're raising a 50kg mass 1.5m above the floor in a gravitational field with 9.8m/s/s. So it means that the work done is 50kgX1.5mX9.8m/s/s=735 joules

b) the work done is converted to potential energy within the gravitational field, so the potential energy = work done = 735 joules

c) likewise, just as the crate impacts the floor, that potential energy gets coverted in full to the kinetic energy such that the kinetic energy = potential energy at 1.5m above the floor = 735 joules

This sounds like your homework..so hope it helps!

Answer 3

Potential energy is given by:

U=m*g*h

where m=object mass, g=acceleration due to gravity (-9.8m/s^2), and h=height of the object.

Generally speaking, this problem is moving the mass from h1 to h2 (where h1=0 and h2=1.5m).

Thus

deltaU=U2-U1
deltaU=m*g*h2-m*g*h1
deltaU=m*g*(h2-h1)
deltaU=m*g*(1.5-0)
deltaU=50*-9.8*1.5
deltaU=-735 J

Now, the work you did (force you applied) to the crate was in the same direction as its motion, so you know that the work done was positive.

W=-U
W=735 J

Kinetic energy is always positive, and is equivalent to the change in potential on the way down. Thus KE=-U, or KE=735J

The other posters have not attempted to reconcile their signs.

Answer 4

(a) Work done = Force x Distance
........................= m xg xh
..........................= 50 x 9.8 x 1.5
..........................= 735 Joules.
(b) Change in PE = Same as work done = 735 Joules
(c) The whole PE is converted into KE = 735 Joules

Answer 5

i have no idea, i'm not a scale.