# Question about Acceleration and rounding curves

• Justincase_

#### Justincase_

So I've just been a bit confused over the concept of rounding curves and accelerating. Obviously its commonly understood that you need an acceleration to maintain a constant speed when rounding a curve, such as turning a vehicle right, left, or making a u turn.

Can anyone help explain why there needs to be some sort of acceleration to round a curve at a constant speed? You can't really round a curve at all with zero acceleration either.

To turn a corner you need to increase your velocity in the transverse direction, that is, the direction at a 90 degree angle to the direction you're currently travelling. If you're traveling in a straight line, this velocity is by definition zero. Increasing it is an acceleration.

Could you be a little more well defined by what you mean when you say "constant speed". For example do you mean the reading on a speedometer of a vehicle?

A simple answer (which is probably not the one you want) is that acceleration is a vector so if a vehicle changes direction, it must be under some form of acceleration.

If you don't accelerate sideways, you will just keep moving forward - no curve.

If you're going in a straight line, you have zero velocity to the right or left and all your velocity in the "straight ahead" direction. If you want to curve, you need to gain some velocity to the right or left. To gain velocity, you have to accelerate.

Now, if you want your total velocity to remain the same, you need to take away some of your "straight ahead" velocity when you add some "right or left" velocity. This would involve deceleration.

So there is a lot of acceleration involved!