A student librarian lifts a 2.2 kg book from the floor to a height of 1.25 meters. Her carries the book 8.0 meters to the stacks and places the book on a shelf that is 0.35 meters above the floor. How much work does he do on the book?
I'm having trouble understanding this problem.
Please help me.
2007-01-12 13:34:04 · 2 answers · asked by vicky p 1 in Science & Mathematics ➔ Physics
2.2Kg*9.8m/s = 21.56N
21.56N*1.25m = 26.95J
We're only concerned with the work done against gravity, lifting the books to 1.25 meters. the distance walked has no effect on the problem, unless you take into account the wind resistance and the force needed to overcome it. Also, lowering the books onto the shelf doesnt count, because gravity does the work on the books.
2007-01-12 13:50:29 · answer #1 · answered by Steve-o 3 · 0⤊ 0⤋
Work W is done against gravity in raising the book from the floor to a final vertical height of 0.35 m.
W =mgh
where, m=2.2 Kg; g=9.81m/s^2; h=0.35m, so
W=2.2*9.81* 0.35 Joules.
Please complete the calculations.
2007-01-12 14:47:08 · answer #2 · answered by Anonymous · 1⤊ 0⤋
WD = mgh = 2.2 x 9.8 x .35 = 7.55 J
Final height is important, not 1.25 m.
2007-01-12 14:31:18 · answer #3 · answered by hello 6 · 2⤊ 0⤋