Laws of Motion Lecture Flashcards

Comprehensive practice flashcards covering forces, Newton's three laws of motion, linear momentum, and universal gravitation as presented in the lecture notes.

What are the two main effects a force can produce on a body according to the transcript?

1. It can change the state of rest or motion (produce acceleration). 2. It can change the size or shape (dimensions) of the body.

List the examples of contact forces provided in the syllabus scope.

Frictional force, normal reaction force, tension force as applied through strings, and force exerted during collision.

List the three types of non-contact forces identified in the notes.

Gravitational, electric (electrostatic), and magnetic forces.

How does the magnitude of non-contact forces depend on the distance of separation?

It varies inversely as the square of the distance of separation ($F \times \frac{1}{r^2}$); doubling the distance makes the force one-fourth.

State Newton's first law of motion.

If a body is in a state of rest, it will remain in the state of rest and if it is in the state of motion, it will remain moving in the same direction with the same speed unless an external force is applied on it.

How is 'force' qualitatively defined based on Newton's first law?

Force is that external cause which tends to change the state of rest or the state of motion of an object.

What is 'inertia' and what factor determines its magnitude?

Inertia is the inherent property of a body to resist change in its state of rest or motion; it is measured by the mass of the body (greater mass equals greater inertia).

Explain why a passenger falls backwards when a train suddenly starts moving forward.

The lower part of the body moves with the train, but the upper part remains at rest due to inertia of rest, causing the passenger to be left behind.

Give an example of inertia of motion from the transcript.

A passenger leaning forward when a running car stops suddenly, because the upper body remains in motion due to inertia while the lower body stops with the car.

Define linear momentum ($p$) and state its mathematical expression.

Linear momentum is the product of mass and velocity, expressed as $p = m \times v$.

What are the S.I. and C.G.S. units of linear momentum?

The S.I. unit is $\text{kg font-size: small; m s}^{-1}$ and the C.G.S. unit is $\text{g cm s}^{-1}$.

State Newton's second law of motion in terms of momentum.

The rate of change of momentum of a body is directly proportional to the force applied on it and takes place in the direction in which the force is applied ($F = \frac{\triangle p}{\triangle t}$).

What is the relation between Newton ($N$) and dyne ($\text{dyne}$)?

$1 \text{ newton} = 10^5 \text{ dyne}$.

Why does a cricketer withdraw his hands along with the ball while catching it?

To increase the time ($t$) to stop the ball, which reduces the rate of change of momentum and thus the force ($F$) exerted on the hands, avoiding injury.

State Newton's third law of motion.

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

Identify the action and reaction forces when a bullet is fired from a gun.

Action is the force exerted on the bullet; reaction is the recoil force experienced by the gun.

State the Universal Law of Gravitation and its equation.

The force of attraction between two particles is directly proportional to the product of their masses and inversely proportional to the square of the distance between them: $F = G \frac{m_1 \times m_2}{r^2}$.

What is the value of the universal gravitational constant ($G$)?

$6.67 \times 10^{-11} \text{ N m}^2 \text{ kg}^{-2}$.

Define acceleration due to gravity ($g$) and provide its mean value on the Earth's surface.

The rate at which the velocity of a freely falling body increases due to Earth's gravitational pulling; its mean value is $9.8 \text{ m/s}^2$.

What is the formula relating $g$ and $G$?

$g = \frac{G \times M}{R^2}$, where $M$ is the mass and $R$ is the radius of the planet.

What are the three equations of motion for a body falling freely from rest ($u = 0$)?

(i) $v = g \times t$, (ii) $h = \frac{1}{2} \times g \times t^2$, (iii) $v^2 = 2 \times g \times h$.

Contrast mass and weight based on the transcript.

Mass is the quantity of matter (scalar, constant); weight is the force of Earth's attraction (vector, varies by location: $W = m \times g$).

Define 1 kilogram force ($kgf$) and its relationship to Newtons ($N$).

1 kgf is the force due to gravity on a mass of $1 \text{ kg}$; $1 \text{ kgf} = 9.8 \text{ N}$.