Question

When no force acts on the body, it must be___.

Answer 1

When the net force equals zero, this obeys Newton’s second law of motion. The body cannot be accelerated. However, mass can never be zero, so acceleration will be zero. The body will be either in uniform motion or the body is at rest.

Complete step-by-step solution:
Given: no force acts on the body.
$F=0$ ……($1$)
Using newton’s second law,
$F = ma$ ……($2$)
Comparing ($1$) and ($2$) equations, we get,
$ma = 0$
$\implies a = 0$
This gives that if the balanced force is equal to zero then there is no acceleration.
Now, we will apply first equation of motion,
$v = u + at$
v is final velocity.
u is the initial velocity.
a is acceleration.
Now, $a = 0$, we get,
$v = u$
Final velocity is equal to the initial velocity.
So, the body will be in uniform motion.
If $u = 0$ then $v = 0$
So, in this situation, the body will be at rest.
Hence, we can say that the body will either rest or move in a straight line.

Note: Acceleration is what alters your speed. When there is zero acceleration, the body remains to go at whatever speed it has previously. This speed can include several values, including zero. When speed is zero, the body continues at rest.