Question

The direction of motion of a body is decided by ________ of the body.
This question has multiple correct options.
A. Velocity
B. Acceleration
C. Displacement
D. Speed

Answer 1

Define vector and scalar quantity. The direction is given by only vector quantities. Scalar quantities can only give magnitudes, not direction. Find out which quantities are vector quantities and then define them to get the answer.

Complete step by step solution:
The velocity of a body can be defined as the displacement covered by the body per unit time. Velocity is a vector quantity which gives the magnitude of speed with which the body is moving and also gives the direction in which the body is moving. So, the velocity of an object can give us the direction of motion of the body.
Now, acceleration can be defined as the rate of change of velocity of an object per unit time. The velocity of the particle increases with time in the direction of acceleration. Again, if acceleration is perpendicular to the direction of velocity, then the body moves in a circular path. So, acceleration can also give the direction of motion of a body.
Displacement is a vector quantity giving the position of the object. It does not actually say in which direction the body is moving. So, displacement does not give the direction of motion of a body.
Speed can be defined as the change of position of an object per unit time. Speed is a scalar quantity. Speed only gives us the magnitude, not direction.
So, we can say that velocity and acceleration can determine the direction of the motion of a body.

The correct options are (A) and (B).

Note: Even if a physical quantity is a vector quantity, it might not give the direction of motion of the object. In this question, the displacement is a vector quantity. It has direction and gives the position of an object but it cannot give the direction of motion of the object.