Mechanics Infographic

MECHANICS

⚙️Mechanics

A branch of science that studies the state of rest or motion of bodies under the action of forces.

🏠Rest

If an object does not change its position with respect to its surroundings and time.

Example: A building, a book on the table.

🚗Motion

If an object changes its position with respect to its surroundings and time.

Example: A moving bus, flowing water.

📈Basic Terms Related to Motion

Distance

The total length of the path traveled by an object.

Scalar

Unit: meter (m)

Displacement

The shortest distance between the initial and final position.

Vector

Unit: meter (m)

Speed

The total distance traveled in a unit of time.

Speed = Distance / Time

Scalar

Unit: m/s

Velocity

The total displacement of an object per unit of time.

Velocity = Displacement / Time

Vector

Unit: m/s

Acceleration

The rate of change of velocity.

a = (v-u) / t

Vector

Unit: m/s²

🚦Types of Motion

Uniform Motion

An object covers equal distances in equal intervals of time.

Example: A car moving along a straight line at a constant speed.

Non-Uniform Motion

An object covers unequal distances in equal intervals of time.

Example: A car moving in traffic signals and crowded paths.

🧮Equations of Motion

For an object moving in a straight line with uniform acceleration:

v = u + at
s = ut + ½at²
v² = u² + 2as

Where:

u = initial velocity (m/s)

v = final velocity (m/s)

a = acceleration (m/s²)

t = time (s)

s = distance traveled (m)

🔄Circular Motion

Uniform Circular Motion

When an object moves with a uniform speed in a circular path.

Example: Hands of a clock, motion of the moon around the Earth.

Concepts of Circular Motion

Angular Displacement

The angle through which the object rotates. Unit: radians (rad).

Angular Velocity (ω)

The rate of change of angular displacement. Unit: radians/sec.

Angular Acceleration (α)

The rate of change of angular velocity. Unit: rad/sec².

Angular Momentum

Product of linear momentum and perpendicular distance from the axis of rotation.

💪Force

Force: A Push or a Pull

A force is a vector quantity with the SI unit of Newton (N).

Effects of Force: It can change the direction, shape, size, or state of motion/rest of an object.

Example: Pulling a door, pushing a cart.

Forces in Circular Motion

Centripetal Force

The net force acting towards the centre of a rotating object. It keeps the object in its circular path.

Example: Planets orbiting the sun, a spinning ball on a string.

Centrifugal Force

The apparent force acting away from the centre. It is an effect of inertia.

Example: Cream separator, mud flying off a tyre.

🍎Newton’s Laws of Motion

Core Concepts

Inertia

The property of a body to oppose any change in its state of motion or rest.

Example: Moving forward when brakes are applied suddenly.

Momentum (P)

The product of mass and velocity. It is a vector quantity. (P = m × v)

Unit: kg-m/s

Impulse (I)

A large force acting on a body for a short interval of time. (I = F × t)

Example: Kicking a ball.

Newton’s First Law (Law of Inertia)

“A body stays in a state of rest or uniform motion unless acted upon by an external unbalanced force.”

Newton’s Second Law

“The force produced by an object is directly proportional to the product of its mass and acceleration.” It’s also the rate of change of momentum.

F = m × a

Newton’s Third Law

“For every action, there is an equal and opposite reaction.”

Example: Recoil of a gun, rocket propulsion, swimming.

Law of Conservation of Momentum

Based on Newton’s Third Law, it states: “In the absence of an external force, the total momentum of a system remains constant.”

Example: Space rocket propulsion.

🔧Other Key Concepts

Friction

The force resisting the relative motion between two surfaces in contact. It’s often called a necessary evil.

Torque

A force that causes an object to rotate. It is a vector quantity with the unit of Newton-meter (N-m).

💡Important Points

  1. Newton’s First Law is known as the Law of Inertia.
  2. Swimming applies Newton’s Third Law.
  3. If distance and time are in equal proportion, it is uniform speed.
  4. Newton gave the laws of motion.
  5. Energy conservation: Energy can neither be created nor destroyed.
  6. Dyne-second is a unit of momentum.
  7. Velocity of a body can be calculated by distance/time.
  8. 1 Newton equals 10⁵ dyne.
  9. Conservation of momentum is related to Newton’s 3rd Law.
  10. Newton’s 1st Law is also called the law of inertia.
  11. The equation for the second law of motion is F = M.A.
  12. The force causing rotation about an axis is called Torque.
  13. Angular displacement is measured in Radians.
  14. The unit of angular velocity is Rad/sec.
  15. “For every action there is an equal reaction” is Newton’s 3rd Law.
  16. Momentum is the product of mass and velocity.
  17. In conservation of momentum (isolated system), total momentum remains constant. (Note: Text says Zero, constant is more accurate).
  18. The property opposing a change in state is called Inertia.
  19. A rocket works on the principle of Law of conservation of momentum.
  20. Angular acceleration is measured in Rad/sec².
  21. Forces on a rotating body are Centripetal and Centrifugal.
  22. Average speed = Total distance / Time taken.
  23. The unit of speed is m/s.
  24. The unit of acceleration is m/s².
  25. Formula for acceleration is a = (v-u)/t.
  26. Formula of velocity is D/t.

Check Your Knowledge (MCQs)

1. What is the SI unit of force

  • a. Newton
  • b. dyne
  • c. poundal
  • d. joule

2. What remains constant in uniform circular motion

  • a. speed
  • b. velocity
  • c. displacement
  • d. none

3. What is the acceleration of a body moving with uniform velocity

  • a. zero
  • b. maximum
  • c. minimum
  • d. none

4. The Newton’s first law is also called as

  • a. law of moments
  • b. law of inertia
  • c. law of energy
  • d. law of conservation

5. Forces are defined by

  • a. Newton’s first law of motion
  • b. Newton’s second law of motion
  • c. Newton’s third law of motion
  • d. none of the above

6. Working of a rocket is based on the principle of

  • a. conservation of momentum
  • b. conservation of mass
  • c. conservation of energy
  • d. conservation of angular momentum

7. The product of mass and velocity measures

  • a. Force
  • b. momentum
  • c. acceleration
  • d. energy

8. According to the law of motion action and reaction always act on

  • a. same body
  • b. acts on the different bodies
  • c. both a and c
  • d. none

9. If an object covers equal distance in equal intervals of a time is said to be

  • a. uniform motion
  • b. uniform velocity
  • c. displacement
  • d. none

10. Rate of change of momentum is directly proportional to

  • a. acceleration
  • b. force
  • c. work
  • d. momentum

11. For every action there is an equal and opposite reaction is stated by

  • a. Newton’s first law of motion
  • b. Newton’s second law of motion
  • c. Newton third law of motion
  • d. law of momentum

12. The rocket works on the principle of

  • a. third law of motion
  • b. conservation of linear momentum
  • c. upthrust
  • d. all of the above

13. The inertia of a body depends on

  • a. mass
  • b. velocity
  • c. acceleration
  • d. length

14. Force can cause a

  • a. change in state of motion
  • b. direction of motion
  • c. shape and size of object
  • d. all of the above

15. What is called change in position in a particular direction of an object

  • a. velocity
  • b. acceleration
  • c. displacement
  • d. distance

16. The rate of change of velocity is called

  • a. acceleration
  • b. force
  • c. momentum
  • d. impulse

17. Centripetal force acts along

  • a. radius towards the centre of circle
  • b. radius away from the centre of circle
  • c. tangent to the circle
  • d. radially to the circle

18. What is the SI unit of momentum

  • a. kg -m
  • b. kg-m/s
  • c. kg-s
  • d. kg-m/s^2

19. If the force acting on a body is doubled what happens to the acceleration

  • a. doubled
  • b. increases by four times
  • c. constant
  • d. half

20. In vacuum all freely falling bodies have the same

  • a. speed
  • b. velocity
  • c. acceleration
  • d. momentum

21. Cream get separated out of milk when it is churned because of

  • a. centrifugal force
  • b. centripetal force
  • c. fractional force
  • d. gravitational force

22. A stationary body can have

  • a. velocity
  • b. momentum
  • c. energy
  • d. acceleration

23. The equation of relation between force mass and acceleration is

  • a. a=mf
  • b. m=af
  • c. ma=1/f
  • d. ma=f

24. Newtons second law gives the definition

  • a. energy
  • b. momentum
  • c. mass
  • d. force

25. Large force acting on body for short time measures

  • a. momentum
  • b. impulse
  • c. force
  • d. torque
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