Question

An object is moving at a constant speed along a straight line. Which of the following statements is not true? A. There must be a non-zero net force acting on the object.
B. The acceleration of the object is zero.

C. The net force acting on the object must be zero.

D. The velocity of the object is constant.

Answer 1

Answer:

False statement = There must be a non-zero net force acting on the object.  

Explanation:

An object is moving at a constant speed along a straight line. If the speed is constant then its velocity must be constant. We know that the rate of change of velocity is called acceleration of the object i.e.

$a=\dfrac{dv}{dt}$

a = 0

⇒ The acceleration of the object is zero.

The product of force and acceleration gives the magnitude of force acting on the object i.e.

F = m a = 0

⇒  The net force acting on the object must be zero.

So, the option (a) is not true. This is because the force acting on the object is zero. First option contradicts the fact.