A small rubber ball is attached to a string. A student swings the ball around her head at a steady speed. What happyans to the speed of the ball if the length of the string is shortened??Explain your answer.
2007-01-04 17:42:58 · 5 answers · asked by Sapan P 1 in Science & Mathematics ➔ Physics
The speed will decrease. If the rate is the same (say 1 revolution per sec), the ball is traveling the circumfance of the circle of 2πr/sec (That's 2 pi r)
If string is getting shorter, then the radius gets smaller so the distance per second is less, which means it is slower.
Think of when you were on the merry-go-round when you were a kid. The fastest part was the very outside and the closer you got to the centre, the slower you went, though the revolutions/minute were the same.
2007-01-04 17:52:43 · answer #1 · answered by borscht 6 · 0⤊ 0⤋
Is this supposed to be a trick question? Because, logically, the speed would stay the same if the student is swinging the ball around her head at a steady speed.
2007-01-04 18:01:38 · answer #2 · answered by chicaSM 1 · 0⤊ 0⤋
Assuming the rotation is constant, the speed of the ball slows as the string shortens. The reason. One revolution with a long string is more distance than one revolution with the short string. If you say that the length of the string is half the original length, say originally 2 meters, shortened to 1 meter. The distance traveled in on revolution for first is 2*pi*r squared, which is 25.1 meters per revolution. The shorter string would be 6.3 meters per revolution. If it takes 1 second to do one revolution then the first speed is 25.1 meters per second, and the second 6.3 meters per second
2007-01-04 17:51:24 · answer #3 · answered by Michael C 3 · 0⤊ 0⤋
The speed of the ball increases. This is a result of the conservation of angular momentum; Angular momentum of the ball on the string is mvr, to maintain this constant, if r is reduced, v must go up. This principle is used by ice skaters in a spin; they start the spin with arms outstretched, then draw their arms close to their bodies to reduce moment of inertia and increase angular velocity.
2007-01-04 17:50:25 · answer #4 · answered by gp4rts 7 · 0⤊ 0⤋
It will be reduced because the propelling force is going to be reduced as the distance or from the center to the arch or circle is reduced.
2007-01-04 17:55:46 · answer #5 · answered by zajil 2 · 0⤊ 0⤋