Q: What is linear momentum?

Linear momentum $\vec{p}$ of a body is defined as the product of its mass and velocity, $\vec{p} = m\vec{v}$.

Q: Write the mathematical form of Newton's Second Law for constant mass.

For constant mass, Newton's Second Law reduces to $\vec{F}_{net} = m\vec{a}$.

Question 1

What is Newton's First Law of Motion?

Accepted Answer

Newton's First Law states that a body remains at rest or in uniform straight-line motion unless acted upon by a net external force; this is called the law of inertia.

Question 2

What is Newton's Second Law of Motion?

Accepted Answer

Newton's Second Law states that the rate of change of momentum of a body is proportional to the applied net force and takes place in the direction of the force, $\vec{F} = \frac{d\vec{p}}{dt} = m\vec{a}$.

Question 3

What is Newton's Third Law of Motion?

Accepted Answer

Newton's Third Law states that for every action there is an equal and opposite reaction; forces always occur in pairs acting on different bodies.

Question 4

What is inertia?

Accepted Answer

Inertia is the property of a body by virtue of which it resists any change in its state of rest or uniform motion in a straight line.

Question 5

What is linear momentum?

Accepted Answer

Linear momentum $\vec{p}$ of a body is defined as the product of its mass and velocity, $\vec{p} = m\vec{v}$.

Question 6

What is impulse?

Accepted Answer

Impulse of a force is the product of force and the time for which it acts and is equal to the change in momentum, $I = F\Delta t = \Delta p$.

Question 7

State the law of conservation of linear momentum.

Accepted Answer

In an isolated system with no external force, the total linear momentum of the system remains constant during any interaction.

Question 8

Write the mathematical form of Newton's Second Law for constant mass.

Accepted Answer

For constant mass, Newton's Second Law reduces to $\vec{F}_{net} = m\vec{a}$.

Question 9

What is an inertial frame of reference?

Accepted Answer

An inertial frame is a reference frame in which Newton's First Law holds, i.e., a frame that is either at rest or moving with uniform velocity.

Question 10

What is a non-inertial frame of reference?

Accepted Answer

A non-inertial frame is a reference frame that is accelerating with respect to an inertial frame, in which fictitious or pseudo forces must be introduced to apply Newton's laws.

Question 11

What is pseudo force?

Accepted Answer

Pseudo force is an apparent force introduced in a non-inertial frame of reference, given by $\vec{F}_{pseudo} = -m\vec{a}_{frame}$, acting opposite to the acceleration of the frame.

Question 12

Define normal reaction.

Accepted Answer

Normal reaction is the contact force exerted by a surface on a body, acting perpendicular to the surface.

Question 13

What is friction?

Accepted Answer

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

Question 14

What are static and kinetic friction?

Accepted Answer

Static friction acts between surfaces at rest relative to each other and can vary up to a limiting value, while kinetic friction acts when surfaces slide over each other with relative motion.

Question 15

What is limiting friction?

Accepted Answer

Limiting friction is the maximum value of static friction just before the body begins to move relative to the surface.

Quantity	Formula	Remarks
Newton II	\(\vec{F}_{\text{net}} = m\vec{a}\)	Constant mass
Impulse	\(\vec{J} = \vec{F}\Delta t = \Delta\vec{p}\)	Impulse–momentum theorem
Static Friction	\(f_s \leq \mu_s N\)	Self-adjusting up to max
Kinetic Friction	\(f_k = \mu_k N\)	μ_k < μ_s always
Banking Angle	\(\tan\theta = v^2/(rg)\)	For frictionless banked road
Max speed (banked)	\(v_{\max} = \sqrt{rg\,\dfrac{\mu_s+\tan\theta}{1-\mu_s\tan\theta}}\)	With friction
Conical Pendulum	\(T = 2\pi\sqrt{L\cos\theta/g}\)	Period
Atwood Machine	\(a = \dfrac{(m_1-m_2)g}{m_1+m_2}\)	Two masses over pulley

Laws of Motion

Core Topics at a Glance

Key Formulae

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