Can an object be accelerating when its speed is zero?

[rfmason_2000]

[bibblebub]

erm, ABerrant, that was me who posted what a vector is after your first posting, not vascop

[vascop]

m
y original answer still holds if you replace the word velocity by speed

[ABerrant]

What is the acceleration rate of a car travelling at an average speed of 0 mph?

[factor-fiction]

Can't say at a particular point, abberant- unless we are sure that the car was stationary. The average speed of zero could reflect a period when it drove in reverse at 10 miles per hour for a minute and then drove forward at 10mph for a minute

[vascop]

Mollykins has got it dead right!

[R1Geezer]

Yes and it's very common. When I'm in my car accelerating my speed is zero, relative to the car. Speed is a relative measure.

[beso]

Those who don't accept Mollykin's and vascop's explanations are misunderstanding the science.

Acceleration is instaneous. It does not require a trend over time. Sensors called (unsurprisingly) accelerometers don't measure the speed twice and calculate the difference. They measure instantaneous acceleration.

In fact Einstein showed us that acceleration is in every way indistinguishable from gravity. In a closed system an observer cannot tell if they are being accelerated or influenced by gravity. So measuring acceleration is no different from weighing an object.

[Barnacle_Bill]

If I remember my physics correctly you can be accelerating towards a point but never get any closer!! That's the case with the planet earth. By virtue of our orbit round the sun we are continually accelerating toward the sun but our velocity in that direction is ALWAYS 0 and our distance always remains the same.

[vascop]

Yes, this is where the distinction between speed and velocity comes in:
if the velocity changes but the speed stays the same then the change is just a change in direction. So if you are whirling a conker round in a horizontal plane on a piece of string and the conker's angular speed is constant, it is still said to be accelerating because its direction of motion (velocity) is constantly changing while its speed remains constant.

[vascop]

I forgot to say Bill that yes, the acceleration is along the string towards the centre of rotation in the same direction as the force.

[vascop]

I wonder what's happened to the original poster?