Question

The state of motion of an object refers to its:
A. Speed and direction of motion
B. Speed only
C. Direction of motion only
D. Neither speed nor direction of motion

Answer 1

Hint: Recall Newton’s first law of motion which states that a body continues to have the same ‘state of motion’ until and unless it is acted upon by an external unbalanced force. Since, we know that force on a body tends to change its velocity, it can be inferred that the state of motion refers to a body’s velocity.

Complete Step-by-Step solution:
The state of motion of a body is described by Newton’s first law of motion which states that a body continues to have the same ‘state of motion’ until and unless it is acted upon by an external unbalanced force. Since, we know that force on a body tends to change its velocity, it can be inferred that the state of motion refers to a body’s velocity.
The velocity of a body refers to its speed and the direction of its motion and hence the state of motion also refers to the speed and the direction of motion of the body, both.
When an external unbalanced force acts upon a body, it produces acceleration (change in velocity per unit time) and thus changes the speed and direction of motion of the body depending upon the direction of the force. Hence, it changes the state of motion of the body.
Hence, the correct option is A) speed and direction of motion.

Note: Newton’s three laws of motion are fundamental to the study of mechanics in general and their proper understanding can help in solving a lot of questions such as this one. All of the three laws have crisp wording and a lot of other related concepts can be kept in mind by understanding the three laws.
A feel for Newton’s first law and the concept of ‘state of motion’ can be obtained by pushing a carrom coin on a very smooth marble floor (or a smooth floor in general). The coin continues to move for a long time and distance with the same velocity unless you give it another nudge, then the direction will be changed and the coin will attain a new ‘state of motion’.