Test: Laws Of Motion - Class 9 MCQ

According to the law of universal gravitation, the gravitational force is inversely proportional to the square of the distance between two masses. If the distance is doubled, the gravitational force becomes one-fourth the original value.

Tension force is a type of contact force that occurs when a string or rope exerts a pull on an object. Unlike non-contact forces such as gravitational or magnetic forces, contact forces require physical interaction between objects.

The gravitational force is always attractive, pulling objects toward each other based on their masses. This is evident in everyday life, such as how the Earth attracts objects toward its center.

The universal gravitational constant (G) is a fixed value (approximately \( 6.67 \times 10^{-11} \, \text{N m}²/\text{kg}² \)) that is used in the formula for calculating the gravitational force between two masses. It enables the quantification of gravitational attraction in various contexts, from planets to everyday objects.

Newton's Second Law states that the force acting on an object is equal to the mass of that object multiplied by its acceleration (F = ma). This means that for a given force, an increase in mass results in a decrease in acceleration.

Inertia of motion refers to the tendency of a moving body to resist changes in its state of motion. For example, a bicycle continues to move forward when pedaling stops until friction or another force brings it to a halt.

According to Newton's Second Law, if the same force is applied to two objects of different masses, the object with greater mass will experience less acceleration. This relationship illustrates how mass and acceleration are inversely proportional when force is constant.

Passengers lurch forward because of inertia, which is the tendency of an object to resist changes in its state of motion. When the car stops suddenly, the passengers' bodies continue to move forward due to their inertia until restrained by the seatbelt.

According to Newton's Second Law (F = ma), the force can be calculated as \( F = 2 \, \text{kg} \times 5 \, \text{m/s}² = 10 \, \text{N} \). This illustrates how force is directly related to both mass and acceleration in motion.

Newton's Third Law states that for every action, there is an equal and opposite reaction. In a rocket launch, the rocket expels gas downward (action), which produces an upward thrust that propels the rocket into the air (reaction). This principle is fundamental in aerospace engineering.

The normal force is the upward force exerted by the table on the book, counteracting the gravitational force acting downward. This force is crucial in maintaining the book's position at rest on the table.

Non-contact forces act at a distance without requiring physical contact. Examples include gravitational, magnetic, and electrostatic forces, which can exert effects over a distance, such as the attraction between magnets or the gravitational pull of the Earth.

Inertia is directly related to mass; a greater mass results in greater inertia, making it more difficult to start or stop motion. For instance, a heavy object like a loaded trolley requires more force to move than a lighter one.

Newton's First Law, also known as the law of inertia, states that a body will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This explains why passengers feel pushed back in their seats when a car accelerates suddenly.

Weight is the force of gravity acting on an object's mass, calculated as \( W = mg \). This means weight varies with the gravitational field strength, while mass remains constant regardless of location.