A solid sphere moves at a terminal velocity of 20 m/s in air at a place where g = 9.8 m/s^2.
A solid sphere moves at a terminal velocity of 20 m/s in air at a place where g = 9.8 m/s2. The sphere is taken in a gravity free hall having air at the same pressure and pushed down at a speed of 20 m/s.
(a) Its initial acceleration will be 9.8 m/s2 downward.
(b) Its initial acceleration will be 9.8 m/s2 upward.
(c) The magnitude of acceleration will decrease as the time passes.
(d) It will eventually stop.
1 Answers
(b) Its initial acceleration will be 9.8 m/s2 upward.
(c) The magnitude of acceleration will decrease as the time passes.
(d) It will eventually stop.
Explanation:
Since there is no gravity there will be no initial acceleration downward, hence the option (a) is wrong.
Since 20 m/s is the terminal velocity, at this velocity the viscous force is equal to the weight of the sphere (assuming the buoyancy force negligible), i.e. it can produce an upward acceleration equal to g = 9.8 m/s². Hence when it is thrown down at 20 m/s, the sphere gets an upward initial acceleration =9.8 m/s². Hence option (b) is true.
Due to upward acceleration, the speed reduces and hence the viscous force. Since the force reduces the magnitude of acceleration also reduces as time passes. Hence option (c) is true.
Since the viscous force opposes the motion of the sphere, it will eventually stop. Hence the option (d) is true.