Question

Correct your friend who says, “ The car rounded the curve at a constant velocity of 70 km/h”.

Answer 1

When an object travels in a rounded curve, the direction of motion keeps changing. So velocity can never be constant in that case. 
The correct sentence would be:
"The car rounded the curve at a constant speed of 70 km/h."

Answer 2

Explanation:

The statement is "The car rounded the curve at a constant velocity of 70 km/h". It is not correct.

On the circular curve, the velocity of the object is keeps on changing because velocity is a vector quantity.

The object moves with a constant speed in the circular path.

So, the correct statement is "The car rounded the curve at a constant speed of 70 km/h”.