Reading: Halloun & Hestenes, Common sense concepts about motion

 From the Mechanics Diagnostic Test (pp. 6a &endash; 6h), answer the following questions by marking the letter of your choice:

 [1] Two balls A and B move at constant speeds on separate tracks. Position occupied by the two balls at the same time are indicated in the figure below by identical numbers. The arrow indicates the direction of motion. Starting points are now shown.

Do the balls ever have the same speed?

(a) Yes, at instant "2." (b) Yes, at instant "5." (c) Yes, at instant "6."

(d) Yest at instants "2." and "6." (e) No.

[3] The accompanying figure shows a ball thrown vertically upwards from point A. The ball reaches a point higher than C. B is a point halfway between A and C(i.e., AB = BC). Ignoring air resistance,

On its way up, what force(s) act on the ball?

(a) Its weight, vertically downward. (b) A force that maintains the motion, vertically upward. (c) The downward weight and a constant upward force. (d) The downward weight and a decreasing upward force. (e) An upward force, first acting alone on the ball from point A to a certain higher point, beyond which the downward weight starts acting on the ball.

[10]The accompanying figure shows a hollow, circular tube laid on a frictionless, horizontal table. You are looking down at the table. A ball is shot into the end A of the tube to leave the other end B at high speed.

Which of the paths below will the ball follow on the table, after it leaves the tube?

[18] The left side of the accompanying figure shows a ball X in motion. The ball slides down an incline AB, then on a frictionless, horizontal track BC. At C, the ball leaves the track. Ignoring air resistance:

A: the same time that ball X in the original figure of part above leaves the tracks at C, and from the same height as C, a ball Y identical to ball X is released from rest to fall vertically downward.

Which ball reaches the ground first?

(a) Ball X. (b) Ball Y. (c) The two balls reach ground at the same time.

(d) It depands on how high C is. (e) None of the above.

 

[31] This figures below show frictionless tracks, set in a vertical plane. A ball is released from rest from the top A at the left side of each of the tracks.

Where is the highest point the ball can reach on the right side of each of the tracks?

(a) Point B which is at the same height as point A. (b) Lower than B.

(c) Higher than B. (d) It depends on how high point A is.

(e) It depends on how big the ball is.