3. A rock is thrown straight up from the earth's surface. Which one of the following statements concerning the net force acting on the rock at the top of its path is true?
(a) It is equal to the weight of the rock.
(b) Because the rock is stationary, it is
instantaneously equal to zero.
(c) Since the direction of travel of the rock changes, its direction changes from up to down.
(d) Since the rock falls, it is greater than the weight of the rock.
(e) It is less than the weight of the rock, but greater than zero.
2007-09-28 11:00:46 · 3 answers · asked by surfing86 2 in Science & Mathematics ➔ Physics
So...which one is the answer..I am officially confused
2007-09-28 11:58:14 · update #1
a because the force is constant
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2007-09-28 11:04:46 · answer #1 · answered by odu83 7 · 0⤊ 0⤋
Because the rock is momentarily stationary, the force of air resistance is zero. The only force acting on the rock is gravity = mg.
2007-09-28 18:24:46 · answer #2 · answered by Alexander 6 · 0⤊ 0⤋
None of these are correct.
Apparently your teacher does not know the difference between "weight" and "force of gravity."
While the rock is in the air, it is weightless.
2007-09-28 18:50:26 · answer #3 · answered by ZikZak 6 · 1⤊ 0⤋