Question

A body is imparted motion from rest to move in a striaght line. It is then obstructed by an opposite force then:

• A. the body may necessarily change direction
• B. the body is sure to slow down
• C. the body will necessarily continue to move in the same direction at the same speed
• D. none of the above

Answer 1

The correct option is B the body is sure to slow down

An opposite force causes retardation, which is the change of velocity with time. Thus the body tends to slow down with time.

The opposite force would thus change the velocity with time as given by

$F=-m\frac{dv}{dt}$