Chapter 2 - "Forces and Laws of Motion"

Study the derivations and practise

What is force?

Force is a push or pull acting on an object. It can change the state of motion, speed, direction, or shape of an object.

What is the SI unit of force?

The SI unit of force is Newton (N).

Is force a scalar or vector quantity?

Force is a vector quantity because it has both magnitude and direction.

What are balanced forces?

Balanced forces are forces acting on an object whose net force is zero. They do not change the state of motion of an object.

What are unbalanced forces?

Unbalanced forces are forces whose net force is not zero. They can change the speed, direction, or state of motion of an object.

What happens when more than one force acts on an object?

When more than one force acts on an object, their combined effect is called the net force or resultant force.

What happens when forces act in the same direction?

Net force = F₁ + F₂. The forces are added because they act in the same direction.

What happens when forces act in opposite directions?

Net force = F₁ − F₂. The direction of the net force is towards the larger force.

What happens when equal forces act in opposite directions?

Net force = 0 N, so the forces are balanced.

What happens when net force is zero?

The object either remains at rest or continues moving with constant velocity in a straight line.

What is frictional force?

Frictional force is a force that opposes the relative motion or tendency of motion between two surfaces in contact.

In which direction does friction act?

Friction acts opposite to the direction of motion or attempted motion.

What is Newton's First Law of Motion?

An object remains at rest or continues to move with uniform velocity in a straight line unless acted upon by an unbalanced external force.

What is Newton's First Law also called?

Newton's First Law is also called the Law of Inertia.

What is inertia?

Inertia is the tendency of an object to resist any change in its state of rest or motion.

What is the relation between mass and inertia?

Mass is a measure of inertia. Greater mass means greater inertia.

What are the three types of inertia?

Inertia of rest, inertia of motion, and inertia of direction.

What is inertia of rest?

The tendency of an object at rest to resist being brought into motion.

What is inertia of motion?

The tendency of a moving object to resist being brought to rest.

What is inertia of direction?

The tendency of an object to resist a change in its direction of motion.

What is Newton's Second Law of Motion?

The rate of change of momentum of an object is directly proportional to the applied unbalanced force and takes place in the direction of the force.

What is the formula for Newton's Second Law?

F = Δp/Δt. For constant mass, F = ma.

What does F = ma mean?

F is force, m is mass, and a is acceleration.

How is force proportional to acceleration?

For constant mass, F ∝ a. If force increases, acceleration increases.

How is acceleration proportional to mass?

For constant force, a ∝ 1/m. If mass increases, acceleration decreases.

How is force related to rate of change of momentum?

F ∝ Δp/Δt. Greater rate of change of momentum means greater force.

What is Newton's Third Law of Motion?

To every action, there is an equal and opposite reaction.

What are the characteristics of action and reaction forces?

They are equal in magnitude, opposite in direction, and act on different objects.

What is momentum?

Momentum is the quantity of motion possessed by an object. It is the product of mass and velocity.

What is the formula for momentum?

p = mv.

What is the SI unit of momentum?

The SI unit of momentum is kg m/s.

Is momentum a scalar or vector quantity?

Momentum is a vector quantity because it depends on velocity, which has both magnitude and direction.

What is the direction of momentum?

The direction of momentum is the same as the direction of velocity.

How is momentum proportional to velocity?

For constant mass, p ∝ v. If velocity doubles, momentum doubles.

How is momentum proportional to mass?

For constant velocity, p ∝ m. If mass doubles, momentum doubles.

What is the relation between force and momentum?

F = Δp/Δt. Force is equal to the rate of change of momentum.

What happens to acceleration if force doubles while mass stays constant?

Acceleration doubles because a ∝ F when mass is constant.

What happens to acceleration if mass doubles while force stays constant?

Acceleration becomes half because a ∝ 1/m.

What happens to momentum if velocity doubles while mass stays constant?

Momentum doubles because p ∝ v.

What happens to momentum if mass doubles while velocity stays constant?

Momentum doubles because p ∝ m.

What is the formula for acceleration?

a = Δv/Δt.

What is the SI unit of acceleration?

The SI unit of acceleration is m/s².

What is the formula for force in terms of mass and acceleration?

F = ma.

What is the formula for force in terms of momentum?

F = Δp/Δt.

What is 1 Newton?

1 Newton is the force required to produce an acceleration of 1 m/s² in an object of mass 1 kg.

What is the key difference between balanced and unbalanced forces?

Balanced forces have zero net force and do not change the state of motion; unbalanced forces have non-zero net force and can change the state of motion.