need help with physics?

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Bergu

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A 102-N sack of grain is hoisted to a storage room 55 m above the ground of a grain elevator
(a) How much work was required?
1 J
(b) What is the potential energy of the sack of grain at this height?
2 J
(c) The rope being used to lift the sack of grain breaks just as the sack reaches the storage room. What kinetic energy does the sack have just before it strikes the ground floor?
3 J
 
Energy = Work

Energy is conserved

Potential Energy @ storage room = Kinetic Energy of falling sack at bottom

PE = MGH
KE = 0.5 MV^2
Work = Force * distance

1)

102 N * 55 m = 5,610 J

or

Weight = 102 N = MG = 10.41 kg

PE = MGH = 10,41 * 9.8 m/s^2 * 55 m = 5610 J

2) 5610 J

3) 5610 J
 
a. The trick for the first one is remembering that mg = weight in newtons

Also, work and energy have the same units, Joules.

finally, N m = J (Newtons multiplied by meters is Joules)

E = mgh = (102 N)(55 m) = 5610 J

b. 5610 J

c. At the moment the sack hits the ground all potential energy has been converted to kinetic energy and so the kinetic energy is 5610 J.
 
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