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EXERCISE 4 : Force and Motion

Force and Motion

Newton’s laws of motion
An object at rest remains at rest, and an object in motion remains in motion at constant speed in a straight line
unless acted on by an unbalanced force. The acceleration of an object depends on the mass of the object and
the amount of force applied. Whenever one object exerts a force on another object, the second object exerts an
equal and opposite on the first.
Newton’s three laws of motion help someone understand how objects behave when standing still, when moving
and when forces act upon them. Sir Newton’s three laws are Newton’s First Law: Inertia, Newton’s Second Law:
Force, Newton’s Third Law: Action & Reaction.

Displacement
Displacement is defined as the change in position of an object. It is a vector quantity and has a direction and
magnitude. It is represented as an arrow that points from the starting position to the final position. For example- If
an object moves from a position to B, then the object’s position changes.
Displacement is the change in the position of an object. It is a vector quantity. The SI unit of displacement is meter
(m).
Displacement can be calculated by measuring the final distance away from a point, and then subtracting the initial
distance. Displacement is key when determining velocity, (which is also a vector). Velocity = displacement/time
whereas speed is distance/time.
Velocity
Velocity is the prime indicator of the position as well as the rapidity of the object. It can be defined as the distance
covered by an object in unit time. Velocity is defined as the rate of change of distance of a body with respect to
time. Its unit in SI is m/s. The different types of velocities are uniform velocity, variable velocity, average velocity
and instantaneous velocity. A body when covers an equal distance with an equal interval of time, this condition
of the velocity is known as uniform velocity. Or, we can say that when the direction and magnitude of speed of a
body do not change with time, then the body is said to be at uniform velocity.
Acceleration
Acceleration is the rate if change if velocity. Usually, acceleration means the speed is changing, but not always.
When an object moves in a circular path at a constant speed, it is still accelerating, because the direction of
its velocity is changing. the SI unit of acceleration is m/ s 2 (meter per sec square).The acceleration can be
positive, negative, or zero depending upon the velocity and its direction. Mainly Uniform acceleration, non-uniform
acceleration, and average acceleration are the three types of accelerated motions. Acceleration (a) is the change
in velocity (Δv) over the change in time (Δt), represented by the equation a= Δv/ Δt. This allows you to measure
how fast velocity changes in meters per second squared (m/s^2). Acceleration is also a vector quantity, so it
includes both magnitude and direction. if you are traveling in a car which is moving at the speed of 60 kmph and
after 1 min the speed of the car is 65 kmph, which means you are accelerating.
Retardation
Retardation is defined as the rate of decrease of velocity with time. Suppose if a car is slowing down, its velocity is
decreasing, so its acceleration is negative. But retardation is positive. Retardation is negative of acceleration. The
SI unit of Retardation (m/s²) meter per second squared. According to the definition, Acceleration can be defined
as the rate of change of the velocity of any object. Retardation is the total opposite of acceleration i.e., negative
acceleration.
Rest & Motion Such As Linear, Angular
Rest: An object is said to be at rest if it does not change its position with respect to its surroundings with time.
Motion: An object is said to be in motion if its position changes with respect to its surroundings and time. A body
may be at rest relative to one object and at the same time it may be in motion relative to another object. For
example, a passenger sitting in a moving bus is at rest with respect to his fellow passenger but he is in motion
with respect to a man standing outside the bus.

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CITS : WCS - Mechanical - Exercise 3