Question

hello,

I need help with this for a homework problem soon. this is just one question with multiple parts i'd greatly appreciate it.

a) (5 pts) During free fall, after some object has been thrown upwards, the velocity momentarily goes to zero at the highest point in the trajectory. Some people (falsely) believe that the acceleration of the object also becomes zero at the highest point in the trajectory. Briefly explain what the motion of the object would look like if the acceleration actually did become zero at the highest point. b) (5 pts) If the acceleration of an object is constant, how are the average velocity and instantaneous velocity related? c) (5 pts) We looked at changing position (displacement and velocity) and changing velocity, but not cases of changing acceleration. How would you know if your motion involved a change in acceleration? d) (5 pts) Explain how someone's average velocity could be zero while their average speed is non-zero (positive, and possibly quite large).

Answer 1

(a) If acceleration also becomes zero at highest point, it means the force acting on the object will reduce to zero at that instant so object will come to at rest.

(b)In case of constant acceleration, instantaneous velocity keeps on changing always but average velocity remains constant.

(c) In case of changing acceleration, force acting on the object will also be changing and the time rate of change of velocity will also be variable.

(d) Average velocity is the time rate of change of displacements and displacement may be zero if the body returns back to starting point so average velocity may be zero but average speed is time rate of change of distance and distance can never be zero hence average speed can never be zero.