LINEAR MOTION KLB PHYSICS FORM 3 NOTES PDF: **Study of motion is divided into two;**

1. Kinematics

2. Dynamics

In kinematics forces causing motion are disregarded while dynamics deals with motion of objects and the forces causing them.

**I. Displacement**

Distance moved by a body in a specified direction is called displacement. It is denoted by letter‘s’ and has both magnitude and direction. Distance is the movement from one point to another. The Si unit for displacement is the metre (m).

**II. Speed**

This is the distance covered per unit time.

Speed= distance covered/ time taken. Distance is a scalar quantity since it has magnitude only.

The SI unit for speed is metres per second(m/s or ms^{-1})

**Average speed**= total distance covered/total time taken Other units for speed used are Km/h.

**Examples**

1. A body covers a distance of 10m in 4 seconds. It rests for 10 seconds and finally covers a distance of 90m in 60 seconds. Calculate the average speed.

**Solution**

**Total distance covered** =10+90= 100m

**Total time taken** =4+10+6= 20 seconds

**Therefore average speed** = 100/20= 5m/s

2. Calculate the distance in metres covered by a body moving with a uniform speed of 180 km/h in 30 seconds.

**Solution**

**Distance covered**=speed*time

=180*1000/60*60=50m/s

=50*30

=1,500m

3. Calculate the time in seconds taken a by body moving with a uniform speed of 360km/h to cover a distance of 3,000 km?

**Solution**

Speed:360km/h=360*1000/60*60=100m/s

**Time**=distance/speed

3000*1000/100

=30,000 seconds.

**III. Velocity**

This is the change of displacement per unit time. It is a vector quantity.

**Velocity**=change in displacement/total time taken

The SI units for velocity are m/s

**Examples**

1. A man runs 800m due North in 100 seconds, followed by 400m due South in 80 seconds. Calculate,

a. His average speed

b. His average velocity

c. His change in velocity for the whole journey

**Solution**

**a. Average speed**: total distance travelled/total time taken

=800+400/100+80

=1200/180

=6.67m/s

**b. Average velocity**: total displacement/total time

=800-400/180

=400/180

=2.22 m/s due North

**c. Change in velocity**=final-initial velocity

= (800/100)-(400-80)

=8-5

=3m/s due North

Source: https://www.advance-africa.com/Physics-Notes-Form-3.html

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