# A car moving with a constant speed of 20m/s is said to have undergone an accelerat

A car moving with a constant speed of 20m/s is said to have undergone an acceleration. Is this possible?

A. yes because the car can be going around a corner
B. no because constant speed means there is no acceleration
C. yes because the direction of the car is also constant
D. no because no time is given

I guessed "B. no because constant speed means there is no acceleration" but I was wrong. :/

Acceleration is a vector with magnitude and direction.It is the rate of change of velocity.
2m/s heading north and 2m/s heading south are not equal so there is change in velocity.
If a body going around a corner, the direction of velocity is changing when entering the corner and with a different direction when exit.

Simon Bridge
Homework Helper

You can travel at a constant speed around a corner ... you just accelerated. Otherwise B and C are actually equivalent statements and there is no reason to pick one or another.

Real pedants will point out that the magnitude of the acceleration can be zero, and grammarians will point out that the car may have accelerated, but is no longer accelerating. Of course, niether of these are options ;)

CWatters
Homework Helper
Gold Member

Understand the difference between speed and velocity. Velocity is a vector that includes a direction component. Speed doesn't.

The expression "constant velocity" would imply constant direction.
The expression "constant speed" leaves open the possibility that the object is changing direction.

A car driving around a circular track at a constant 20mph is moving at constant speed but it's velocity is constantly changing because the direction is changing.

Any change in velocity (either the speed or direction component or both) implies an acceleration and a force.