Question

Name the physical quantity which causes motion in a body?
${\text{A}}{\text{.}}$ Force
${\text{B}}{\text{.}}$ Work
${\text{C}}{\text{.}}$ Energy
${\text{D}}{\text{.}}$ Power

Answer 1

Hint: Here, we will proceed by defining the physical quantities mentioned in the options of the problem (i.e., force, work, energy and power). Then, we will see which one causes motion. Then, we will discuss Newton’s laws of motion.

Complete Step-by-Step solution:
${\text{A}}{\text{.}}$ Force is defined as any action that tends, or distorts, to sustain or modify a body 's motion. The principle of force is generally defined in terms of the three laws of motion invented by Isaac Newton. Due to Newton's first principle, a body in a straight line which is at rest or moving at a constant pace must remain in that state until any force is applied to it. The second law states that when an external force acts on a body it causes the body to accelerate (change in velocity) in the direction of the force. Newton's third law states that when one body exerts a force on another then the second body exerts an equivalent force on the first body . This principle of action and reaction explains why a force tends to deform a body (i.e., change its shape) whether or not it causes the body to move.
Clearly, force is the physical quantity that causes motion in the body.
Therefore, option A is correct.

${\text{B}}{\text{.}}$ Work is the product of force and displacement. A force is said to do positive work if (when applied) the force has a part in the direction of the point of application. A force does negative work if at the point of application of force the force has a part opposite to the direction of the displacement. Work doesn’t cause motion in the body.
So, option B is incorrect.

${\text{C}}{\text{.}}$ Energy is the capacity to do work. It may exist in different forms, including potential, kinetic, thermal, electrical , chemical, nuclear, or other. In addition there is heat and work (energy in moving from one body to another). Energy does not cause movement in a body, either.
So, option C is incorrect.

${\text{D}}{\text{.}}$ Power is the rate at which work is done or the rate at which energy is transferred or converted from one type to another from one position to another. It can also be known as work per unit time. Power does not cause motion in a body, either.
So, option D is also incorrect.

Note- The magnitude of the acceleration according to Newton's second law of motion is directly proportional to the magnitude of the external force and inversely proportional to the amount of matter in the body. This will be mathematically represented as External Force = (Mass)(Acceleration).