# Can an object have zero velocity and still be accelerating? (b) Can an object have a constant velocity and still have a varying speed?

In each case, give an example if your answer is yes; explain why if

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• Anonymous
1 month ago

For the first part, a), the answer is yes. For example, when the  piston in a car reaches the top of it's stroke it is momentarily stationary  but it then reverses direction giving a change in it's velocity's direction  producing an  acceleration.

b) The answer is no. Speed is just how fast a object is moving. However, velocity is speed with direction. if the velocity is constant then by definition both the speed and direction must also be constant too.

• Yes, Velocity is speed in a direction. (10MPh North).

A weight on a string in a circle is speed without direction so velocity is zero.

No, I don't thing so. change speed and velocity changes.

• You have some good answers for a).

For b) I would just want to clarify that that truely constant velocity, ie constant speed and constant direction must be constant speed. However, constant velocity in a given direction can be achieved with varying speed if the direction of the path changes.

• (a) An object could momentarily have zero velocity while accelerating. Acceleration means velocity is changing; it could be changing from -1 to 0 to +1.

(b) Speed is just the magnitude of velocity. If an object has constant velocity, then it has constant speed.

(The opposite is not true: an object can have constant speed and varying velocity if it changes direction)