Laws of Motion Practice Questions

Correct answer: It will continue to move at a constant velocity.

Newton's First Law, or the Law of Inertia, states that an object will maintain its state of rest or uniform motion in a straight line unless compelled to change by an external force. This means in the absence of friction or other forces, its velocity remains constant.

Correct answer: Mass

Mass is the measure of inertia; the greater the mass of an object, the more it resists changes to its state of motion. It is an intrinsic property of the object and does not change regardless of the gravitational field.

Correct answer: They are balanced forces that result in zero net force.

Since the book is at rest, the net force must be zero according to the First Law. The downward gravitational force and the upward normal force are equal and opposite, but they are not an action-reaction pair because they both act on the same object (the book).

Correct answer: Acceleration is directly proportional to the net force applied.

Newton's Second Law is expressed as $F = ma$. This indicates that for a constant mass, the acceleration of an object is directly proportional to the magnitude of the net force and follows the direction of that force.

Correct answer: Inertia of rest

Inertia of rest is the tendency of a body to remain at rest. When the bus moves, the lower part of the body moves with the bus, while the upper part tries to maintain its original position of rest, resulting in a backward jerk.

Correct answer: Quadruple

Using $a = F/m$, if $F$ becomes $2F$ and $m$ becomes $m/2$, the new acceleration is $a' = (2F) / (m/2) = 4(F/m) = 4a$. Therefore, the acceleration increases four times.

Correct answer: Third Law of Motion

Newton's Third Law states that for every action, there is an equal and opposite reaction. When the gun exerts a forward force on the bullet (action), the bullet exerts an equal backward force on the gun (reaction).

Correct answer: kg m/s

Momentum ($p$) is the product of mass ($m$) and velocity ($v$). Since the SI unit of mass is kg and velocity is m/s, the unit for momentum is $kg \cdot m/s$.

Correct answer: 0 N

If an object moves with constant velocity, its acceleration is zero. According to $F = ma$, if $a = 0$, the net force ($F$) must also be zero.

Correct answer: Frictional force

Friction between the tires and the road provides the necessary centripetal force to change the direction of the vehicle. Without sufficient friction, the vehicle would continue in a straight line due to inertia.

Correct answer: Time interval

Impulse is the product of force and the time interval over which that force acts, so it is measured in newton-seconds. It also equals the change in momentum of an object, which is what makes it useful for analyzing collisions and impact forces over short durations.

Correct answer: Increase

When accelerating upward, the scale must provide a normal force greater than the man's weight to create the upward acceleration ($N = mg + ma$). The scale measures this normal force, so the 'apparent weight' increases.

Correct answer: It can be at rest or moving with constant velocity.

Balanced forces mean the net force is zero. According to Newton's First Law, an object with zero net force will either remain at rest or continue to move at a constant velocity in a straight line.

Correct answer: Inertia

Inertia is a property of matter related to mass, which is a scalar quantity. Force, momentum, and acceleration all have both magnitude and direction, making them vectors.

Correct answer: Both experience the same magnitude of force.

According to Newton's Third Law, the force the truck exerts on the car is equal and opposite to the force the car exerts on the truck. However, the car will experience a greater acceleration because it has less mass ($a = F/m$).

Correct answer: Opposite to the direction of motion

Friction is a resistive force that opposes the relative motion or the tendency of such motion between two surfaces in contact. It acts parallel to the surfaces and opposite to the velocity of the object.

Correct answer: Both will hit at the same time.

In a vacuum, the only force is gravity. Since acceleration due to gravity is independent of the mass of the falling object ($g = F/m$), all objects fall with the same acceleration and hit the ground simultaneously.

Correct answer: Linear momentum

Rockets work by expelling gas backward at high velocity. The backward momentum of the gas is balanced by an equal forward momentum given to the rocket, maintaining the total momentum of the system.

Correct answer: The applied unbalanced force

This is the formal statement of Newton's Second Law: $F = dp/dt$. The net force applied to an object is equal to the rate at which its momentum changes over time.

Correct answer: Third Law

To swim forward, a swimmer pushes the water backward (action). The water, in turn, exerts an equal and opposite force on the swimmer, pushing them forward (reaction).