Ten seconds after an electric fan is turned on, the fan rotates at 300 rev/min. its average angular acceleration is
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Answer:
a) vboat = 5.95 m/s b) vriver= 1.05 m/s
Explanation:
a) As observed from the shore, the speed of the boats can be expressed as the vector sum, of the boat speed relative to the water and the river speed relative to the shore, as follows:
vb₁s = vb₁w + vrs
In one case, the boat is moving in the same direction as the water:
vb₁s = vb₁w + vrs = 7.0 m/s (1)
For the other boat, it is clear that is moving in an opposite direction:
vb₂s = vb₂w - vrs = 4.9 m/s (2)
As we know that vb₁w = vb₂w, adding both sides, we can remove the river speed from the equation, as follows:
vb₁w = vb₂w =
b) Replacing this value in (1) and solving for vriver, we have:
vriver = 7.0 m/s - 5.95 m/s = 1.05 m/s
(we could have arrived to the same result subtracting both sides in (1), and (2))
Answer:
This is a conceptual problem so I will try my best to explain the impossible scenario. First of all the two dust particles ara virtually exempt from any external forces and at rest with respect to each other. This could theoretically happen even if it's difficult for that to happen. The problem is that each of the particles have an electric charge which are equal in magnitude and sign. Thus each particle should feel the presence of the other via a force. The forces felt by the particles are equal and opposite facing away from each other so both charges have a net acceleration according to Newton's second law because of the presence of a force in each particle:
Having seen Newton's second law it should be clear that the particles are actually moving away from each other and will not remain at rest with respect to each other. This is in contradiction with the last statement in the problem.