Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Newton's First Law of Motion: An object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied unbalanced force .
Inertia: The natural tendency of objects to resist a change in their state of rest or of uniform motion. This law is also known as the 'Law of Inertia'.
Mass as a Measure of Inertia: Inertia is quantitatively measured by the mass of an object. A heavier object has more inertia and offers more resistance to a change in its state.
State of Equilibrium: If the net external force , the object will maintain its velocity (where can be or a constant value).
Types of Inertia: (1) Inertia of Rest, (2) Inertia of Motion, and (3) Inertia of Direction.
📐Formulae
💡Examples
Problem 1:
Explain why a passenger in a bus falls backward when the bus suddenly starts moving from a state of rest.
Solution:
This happens due to the 'Inertia of Rest'.
Explanation:
When the bus is at rest, the passenger's entire body is at rest. When the bus starts suddenly, the lower part of the body in contact with the bus moves forward, but the upper part tends to remain at rest due to inertia, causing the passenger to fall backward.
Problem 2:
Which has more inertia: a cricket ball or a tennis ball of the same size?
Solution:
The cricket ball has more inertia.
Explanation:
Inertia depends on the mass of the object. Since a cricket ball is denser and has a greater mass (), it offers greater resistance to change in its state of motion.
Problem 3:
A car is moving with a constant velocity of . What is the net force acting on it?
Solution:
Explanation:
According to Newton's First Law, if an object is moving with a constant velocity , its acceleration is . Therefore, the sum of all external forces acting on it must be zero.