(a) Can an object be moving when its acceleration is zero? If so, give an example. (b) Can an object be accelerating when its speed is zero? If so, give an example.
Solution 17E (a) An object can have zero acceleration under two circumstances. Firstly, when the object is at rest, its velocity is also zero. Secondly, when the object moves with a uniform velocity, That means the object has the same velocity during its motion. In this case, there is no change in velocity and the acceleration of the object will be zero. Consider a car moving with a uniform velocity of 100 km/h. Its acceleration is zero, since the velocity is uniform. But it is still in motion despite having zero acceleration. (b) Yes, this situation is also possible. Consider a ball thrown up vertically from ground. Only force acting on it throughout its motion is the gravity. At the highest point, it momentarily stops. So, its speed is zero. But it will continue to be accelerated toward the ground by the earth’s acceleration due to gravity. In this case, despite having a zero speed, the ball will have an acceleration.
