Explanation
$$\large\textbf{Step 1: For the First case}$$
Given,
Force exerted $$=$$ $$200N$$
Mass of the object $$= 40kg$$
Ice sheet is perfectly smooth, Hence friction force is zero here
We know,
$${\bf{Force}}{\rm{ }} = {\rm{ }}{\bf{Mass}}{\rm{ }} \times \;{\bf{Acceleration}}$$
Or $$F = ma$$
Or Acceleration, $$a = \dfrac{F}{m}$$$$=$$ $$\dfrac{{200}}{{40}} = 5m/{s^2}$$
$$\large\textbf{Step 2: For the second case}$$
Total mass $$=$$ $$40+40$$ $$=$$ $$80 kg$$
Force $$=$$ $$200 N$$
So,
Or Acceleration, $$a' = \dfrac{F}{m} = \dfrac{{200}}{{80}} = 2.5m/{s^2}$$
$$\textbf{Hence, in the second case the acceleration is } 2.5m/s^2 $$
Inertia is the property to resist the change in motion. The more the mass of the object, the more is the resistance to the change in velocity.
$$ F = m \times a $$
For same force, if mass is more, then acceleration is less and thus mass is the measure of inertia.
(3) both the magnitude and direction
Explanation:
Force is an external effort in the form of push or pull that can change the speed, direction and shape of the body.
Force always has some direction. The direction in which a body is pushed or pulled is called the direction of force.
Therefore, Force has both magnitude as well as direction.
So, to express it correctly we require both the magnitude and direction.
Hence option (3) is correct.
Correct Answer: D
Momentum defined as the quantity of motion of a body. It is a vector quantity and measured by the product of mass and velocity of the body. So,
momentum = mass ×velocity
$$=m×V=mV$$
Hence Option (D) is the right answer.
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