|Dec8-08, 07:25 PM||#1|
1. The problem statement, all variables and given/known data
A 5.00 kg sack of flour is lifted vertically at a constant speed of 3.50 m/s through a height of 15.0 m.
2. Relevant equations
a) How great a force is required?
b) How much work is done on the sack by the lifting force?
c) What becomes of this work?
3. The attempt at a solution
Originally i assumed that acceleration at constant speed is the same as the speed, but then i realized that acceleration at constant speed is zero.
F=5.00kg * 3.50 m/s
F = 17.5 kg * m/s
so when you include zero in the equation you get that there is no force?
But there has to be some force in order to calculate work
W=F*(15.0m)*Cos(180) ; it would be 180 since its being lifted vertically correct?
|Dec8-08, 07:33 PM||#2|
I think i figured it out right after i typed it... would you use gravity acceleration?
F = 5 kg * -9.8 m/s
F = -49 kg m/s
W = -49 kg m/s * 15.0m * cos(180)
W = 735 J
Does that seem correct?
|Dec8-08, 07:53 PM||#3|
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