what is Kinematics?
Kinematics is the branch of physics which involves description of motion without examining the forces which produce it. It is a study of how changes in motion are linked to time.
1.1 Speed and velocity
Speed is a scalar quantity. It tells us how fast or how slow a body is moving, It describes how the distance of the object changes with time.
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A jumbo jet can fly at a speed of 1000 km/h, i.e. it can travel a distance of 1000 km in 1 hour!
Average Speed
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Due to traffic Conditions, it is unlikely that a moving body will be able to maintain a constant or uniform speed throughout its journey. Hence it is more appropriate to use the term average speed.
Worked Example 1.1
Laith begins cycling from home and reaches his school 12 km away in 30 minutes. Calculate his average cycling speed in (a) km/h; (b) m/s
Solution
(a) average speed = Total distance / total time = 12 km/0.5 h = 24 km/h
(b) 24 km /h = 24 000 m/3600 s = 7 m/s
Kinematics is the branch of physics which involves description of motion without examining the forces which produce it. It is a study of how changes in motion are linked to time.
1.1 Speed and velocity
Speed is a scalar quantity. It tells us how fast or how slow a body is moving, It describes how the distance of the object changes with time.
However, a common snail crawls at an average speed of 0.002 km/h. That's right! it covers a mere distance of 2 meters in 1 hour!
Velocity is a vector quantity. It also tells us how fast or how slow a body is moving. But as a vector quantity, velocity is defined by a magnitude as well as a direction.So velocity is speed in a specific direction.
To investigate the difference between speed and velocity, watch this funny video:
http://www.youtube.com/watch?v=DRb5PSxJerM
Due to traffic Conditions, it is unlikely that a moving body will be able to maintain a constant or uniform speed throughout its journey. Hence it is more appropriate to use the term average speed.
The SI unit of average speed is meter per second (m/s).A more common and convenient unit of speed for our vehicle is kilometer per hour (km/h)
Worked Example 1.1
Laith begins cycling from home and reaches his school 12 km away in 30 minutes. Calculate his average cycling speed in (a) km/h; (b) m/s
Solution
(a) average speed = Total distance / total time = 12 km/0.5 h = 24 km/h
(b) 24 km /h = 24 000 m/3600 s = 7 m/s
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