Question

If the net force on an object is zero then
Group of answer choices

the object's speed can change.

the object must be at rest.

the object's speed is constant but its direction might be changing.

the object has zero acceleration.

Answer 1

Right option is

the object has zero acceleration.

let see in detail:

What is Net Force?

A Net Force is the sum of all forces acting on an object and according to Newtons Second law,

The acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system, and inversely proportional to its mass. In equation form, Newton’s second law of motion is

    

This is often written in the more familiar form

  

it means that Net force is responsible for change in velocity or we can say acceleration of object.

in a given sentence If the net force on an object is zero then

acceleration is also zero because acceleration is zero only when objects velocity is constant or object is at rest(v=0), since acceleration is nothing but change in velocity object.

  

Lets see all the options one by one.

1) the object's speed can change.

it means that object has acceleration but it is impossible in this case, so this is not a right option.

2) the object must be at rest.

if it is the sentence like object may be at rest then we can accept this option but when net force on object is zero then either object is moving with constant velocity or it is at rest, it not only at rest, so this is not a right option.

3) the object's speed is constant but its direction might be changing.

we know that velocity is a vector quantity, that means it depends on both magnitude and direction. when object is moving with constant speed but its direction is changing then velocity is also changing which leads to accelerating the object.this is again impossible in this case, so this is not a right option.

4) the object has zero acceleration.

as we already discussed when net force on object is zero then its acceleration is zero therefore this is the right option.