Question

Which of the following situations is impossible?
A) An object has zero velocity but non-zero acceleration.
B) An object has velocity directed east and acceleration directed east.
C) An object has constant non-zero acceleration and changing velocity.
D) An object has velocity directed east and acceleration directed west.
E) An object has constant non-zero velocity and changing acceleration.

Answer 1

Answer on Question#41007 – Physics – Mechanics

Which of the following situations is impossible?

A) An object has zero velocity but non-zero acceleration.

B) An object has velocity directed east and acceleration directed east.

C) An object has constant non-zero acceleration and changing velocity.

D) An object has velocity directed east and acceleration directed west.

E) An object has constant non-zero velocity and changing acceleration.

Solution:

All situations are possible instantaneous initial states, but only (a,c) are not possible quasi-steady final states.

Instantaneous initial state examples:

A) an object has zero velocity but nonzero acceleration

Car at rest, step on accelerator.

B) an object has constant nonzero acceleration and changing velocity

Object in freefall

C) an object has constant nonzero velocity and changing acceleration

Car cruising at 55mph; step on brakes or gas.

D) an object has velocity directed east and acceleration directed west

Car traveling east, step on brakes.

E) an object has velocity directed east and acceleration directed east

Car traveling east, step on gas.

Thus, all situations possible.

If this question is referring to the condition/situation as a quasi-steady final state (rather than an instantaneous one) then

A) an object has zero velocity but nonzero acceleration

Not possible: non-zero acceleration will eventually produce a velocity:

B) an object has constant nonzero acceleration and changing velocity

Possible: object in freefall

C) an object has constant nonzero velocity and changing acceleration

Not possible: velocity cannot be constant in the presence of a non-zero acceleration.

D) an object has velocity directed east and acceleration directed west

Possible: car moving east hits the brakes.

E) an object has velocity directed east and acceleration directed east

Possible: car moving east hits the accelerator.

So (A, C) are not possible quasi-steady final states.

**Answer**: impossible situations:

A) An object has zero velocity but non-zero acceleration.

C) An object has constant non-zero acceleration and changing velocity.

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