The figure below shows a block attached to a pulley and a string.
1) which quantity has essentially the same nonzero value at all three points?
2) which quantity changes direction at point Z?
3)which quantity is zero at point Y?
Restoring force = -kx, where k is constant and x is the distance from equilibrium.
Force of gravity = mg, where m is mass and g is acceleration due to gravity.
KE=½mv^2, where m is mass and v is velocity.
Velocity= distance over time
Net force equal mass times acceleration.
The Attempt at a Solution
1) Force of gravity acting on the block is the same, since mass didn’t change and g is always constant. D then.
I have a question here.Because Y is midway, does that mean it’s the equilibrium position?
2) I doubt my answer here. KE is a scalar, so no change in direction. Force of gravity is always downward. That leaves A, B, and E.
The force on the string is the restoring force that is always pulling the mass to its equilibrium position. So, if it is at point Z the restoring force pulls it upward to its equilibrium position. If it’s at point X, restoring force pulls it downward to its restoring position.
For velocity, the object is changing its direction when it oscillates between X and Z. Not sure what happens to direction of the acceleration. All I know is that, at equilibrium position, velocity is maximum while acceleration is zero, but for direction I guess it changes direction as the velocity? But I chose E.
3) I learned that at maximum distance, X and Z, the restoring force and the acceleration are maximum while velocity is zero. At equilibrium position, velocity is maximum while acceleration and restoring force are zero. If Y is the equilibrium position, there’s two possible answers, A and E. I thought of the acceleration of the system as a nonzero constant. If Y is not the equilibrium position, so it is B. Confusing..
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