Chapter 8 : “Motion”
KEY CONCEPTS [ *rating as per the significance of concept ]
1 Motion ****
2 Graphical Representation of Motion ***
& Graphs
3 Equation of motion ****
4 Uniform Circular Motion **
1 Motion (Uniform Motion And Non Uniform Motion, Acceleration and Velocity)
A particle is a point-like object, has mass but infinitesimal size
The object’s position is its location with respect to a chosen reference point, In
the diagram, the road sign the reference point
Motion occurs when an object changes its position.
Both Distance and Time are important in describing motion.
Sometimes you know motion has occurred even if you didn’t see it happen.
(mail truck)
Relative motion: when two objects are moving in a plane (either in same
direction or opposite) each have relative motion with respect to second. e.g. a
person sitting in a train and watching a tree, in this case tree is stable but is
assumed to be moving but with respect to train.
Distance vs. Displacement
• Distance: How far an object has moved. It has only magnitude without
direction. (total)
• Displacement: How far and in what direction an object has moved from its
start position. i.e. the direct distance between two points.
Speed
Speed = the distance an object travels in a given amount of time
Speed =
sI unit of speed is m/s
96
, Types of Speed
Constant speed: speed doesn’t change (set your car on cruise control)
Changing speed: Riding a bike for 5 km. Take off and increase speed, slow
down up hill, speed up down hill, stop for stop sign. The trip took you 15 min
(.25 h)
Average speed:
Instantaneous speed: speed at any given time.
Velocity
Velocity: includes speed and DIRECTION
Storm is moving at 20km/hr.
Should you be seeking shelter?
Suppose two trains are going with the same speed in opposite direction so
they are having different velocities.
Race car going around an oval track might have constant speed, but
different velocities at each point.
Acceleration
Any change in velocity over a period of time is called acceleration.
The sign (+ or -) of indicates its direction. + sign shows the acceleration and –
sign shows de-acceleration.
Uniform (constant) acceleration equation
a = v/t
97
KEY CONCEPTS [ *rating as per the significance of concept ]
1 Motion ****
2 Graphical Representation of Motion ***
& Graphs
3 Equation of motion ****
4 Uniform Circular Motion **
1 Motion (Uniform Motion And Non Uniform Motion, Acceleration and Velocity)
A particle is a point-like object, has mass but infinitesimal size
The object’s position is its location with respect to a chosen reference point, In
the diagram, the road sign the reference point
Motion occurs when an object changes its position.
Both Distance and Time are important in describing motion.
Sometimes you know motion has occurred even if you didn’t see it happen.
(mail truck)
Relative motion: when two objects are moving in a plane (either in same
direction or opposite) each have relative motion with respect to second. e.g. a
person sitting in a train and watching a tree, in this case tree is stable but is
assumed to be moving but with respect to train.
Distance vs. Displacement
• Distance: How far an object has moved. It has only magnitude without
direction. (total)
• Displacement: How far and in what direction an object has moved from its
start position. i.e. the direct distance between two points.
Speed
Speed = the distance an object travels in a given amount of time
Speed =
sI unit of speed is m/s
96
, Types of Speed
Constant speed: speed doesn’t change (set your car on cruise control)
Changing speed: Riding a bike for 5 km. Take off and increase speed, slow
down up hill, speed up down hill, stop for stop sign. The trip took you 15 min
(.25 h)
Average speed:
Instantaneous speed: speed at any given time.
Velocity
Velocity: includes speed and DIRECTION
Storm is moving at 20km/hr.
Should you be seeking shelter?
Suppose two trains are going with the same speed in opposite direction so
they are having different velocities.
Race car going around an oval track might have constant speed, but
different velocities at each point.
Acceleration
Any change in velocity over a period of time is called acceleration.
The sign (+ or -) of indicates its direction. + sign shows the acceleration and –
sign shows de-acceleration.
Uniform (constant) acceleration equation
a = v/t
97
