# True/False: velocity, motion, gravity, mass

The average velocity of a car traveling with a constant acceleration during a certain time interval is equal to the mean of the velocities at the beginning and end of that time interval.

True

False

Free-fall is the motion of an object subject only to the influence of gravity.

True

False

Mass is a vector quantity.

True

False

https://brainmass.com/physics/gravity/true-false-velocity-motion-gravity-mass-112772

#### Solution Preview

The average velocity of a car traveling with a constant acceleration during a certain time interval is equal to the mean of the velocities at the beginning and end of that time interval.

True

The average velocity is given by the total displacement X over time period ...

#### Solution Summary

With explanations and calculations, the three true false questions are solved.

Atwood machine & rotating rods questions

The first question involves an atwood machine, the second involves two different rods attached to hinges falling/rotating to the ground.

See the jpeg for exact questions. The text is provided below simply for the benefit of the search engine:

Atwood Machine

A frictionless pulley with mass Mb is attached to the ceiling, in a gravity field g. Mass Mc is smaller than mass Ma. The tensions Tx, Ty, Tz, and the constant g are magnitudes. For each statement, select a response. Motion of Masses on a Pulley.

Greater than Less than Equal to True False Ty is .... Tz +Tx.

Greater than Less than Equal to True False Tz is .... Tx.

Greater than Less than Equal to True False (Ma+Mc+Mb)g is .... Ty.

Greater than Less than Equal to True False The magnitude of the acceleration of Ma is .... that of Mc.

Greater than Less than Equal to True False The center-of-mass of Ma, Mc, and Mb does not accelerate.

Greater than Less than Equal to True False Tz is .... (Mc)g.

Rotating Rods

Two uniform rods are connected to a table by pivots at one end. Rod B is longer than rod A. Both are released simultaneously from an initial angle q as shown in the figure. Notation: CM = center of mass; a = angular acceleration; ax = magnitude of horizontal acceleration; ay = magnitude of vertical acceleration. For each of the following statements, determine whether it is correct or incorrect.

Correct Incorrect ax of the CM initially equals 0 for both rods.

Correct Incorrect The density of the rods affect their rate of fall.

Correct Incorrect aA and aB are the same initially.

Correct Incorrect Just before landing, the CM of B has a smaller speed than the CM of A.

Correct Incorrect Rods A and B hit the ground at the same time.

Correct Incorrect aA and alphaB both increase with time.

Correct Incorrect aA and aB are dependent on q.

Correct Incorrect ay is initially equal for the CM of A and B.