Basic Terminologies of Physics
1. Distance & Displacement
- Distance is the path sequence between the starting point and the endpoint. i.e. how much ground an object has covered.
- Distance is a scalar quantity.
- Displacement is the shortest distance between the starting point and the endpoint. i.e., speed = move + direction.
- Displacement is a vector quantity.
- The displacement is less than the distance, or the Same.
- SI: m & CGS: cm
- The distance traveled by an object in a certain direction over a period of time is called velocity.
- Velocity = displacement / time
v = Displacement(d)/Time(t)
- SI: m/s & CGS: cm/s
- The change in velocity over a period of time is called acceleration.
- Acceleration = v-u / t = velocity change / time = final velocity - start velocity / total duration
a = u-v/t
- If the velocity decreases, then there is a negative acceleration. If the velocity increases, then there is a positive acceleration.
4. Other formulas for motion
Speed - Time relationship
v = u+at
Displacement - Time relationship
s= ut + ½ at2
Displacement - Velocity relationship
v2 = u2 + 2as
Inertia is the state of resisting a change in the stationary or moving state of an object.
Inertia at rest
The inertia of rest is the tendency of a body to resist a change of state of motion from rest by an external force.
- When the bus starts suddenly, the passenger falls backward.
- After moving the branch, the fruit fell from the tree.
- After shaking the shatranj, the dust particles remain still, so the shatranj becomes clean
Inertia due to Motion
The resistance that occurs when the motion of an object is brought to a state of rest is called Inertia due to Motion.
- Even if the fan button is turned off, it rotates. (Some time)
- The passenger getting off the moving bus falls forward
- When the bus suddenly stops, the passenger leans forward.
Inertia due to Direction
The property of an object that resists changing the direction of its motion is called inertia of direction.
- When the vehicle is moving, the mud blows upwards.
- While sharpening the knife, sparks are seen flying from the tangent of the sharpening wheel.
6. Newton's laws of motion
The first law - the law of inertia
When no external force acts on the main object, then the object in the state of rest remains in the state of rest, while the object in the state of motion remains in the state of motion, this is called the law of inertia.
The second law - the law of force
The acceleration of an object depends on the mass of the object and the amount of force applied.
force = mass X acceleration
- Hitting the ball with the bat.
- Flight of ‘Agni’ Missiles
The third law - Action & Reaction
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. The rate of change of momentum is proportional to the force applied. Also, the change of momentum is in the direction of the force.
momentum (p) = mass (m) X speed (v)
- In the game of cricket, a player withdraws his hand when caught.
- Because of his arm and the speed of the ball - as their duration increased. This reduces the momentum of the ball and reduces the impact on the hand.
- In the high jump arena, the player falls on a thick layer of sand.
- The motion of a jet engine produces thrust.
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