Kinematics
Motion in a straight line and in a plane, relative velocity and projectiles.
What is Kinematics?
Description of motion through position, displacement, velocity and acceleration, without reference to forces
Key formula / rule: Equations of motion
Key points
- Use the equations of motion and read velocity-time and position-time graphs by slope and area
Common exam trap
Using v = u + at when acceleration varies
Definitions
- Name
Kinematics
- Definition
Description of motion through position, displacement, velocity and acceleration, without reference to forces
- Name
Key idea
- Definition
On a velocity-time graph the slope is acceleration and the area is displacement; on a position-time graph the slope is velocity
- Name
Exam insight
- Definition
Graph questions are solved by slope-and-area reasoning alone; relative velocity uses vAB = vA - vB
- Name
Worked example
- Definition
From rest with a = 2 m/s2 for 5 s: v = u + at = 10 m/s, s = ut + (1/2)at2 = 25 m (triangle area on the v-t graph)
Learning objectives
Use the equations of motion and read velocity-time and position-time graphs by slope and area
Formulae
- Name
Equations of motion
- Expression
v = u + a t; s = u t + (1/2) a t2; v2 = u2 + 2 a s
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Relative velocity
- Expression
vAB = vA - vB
Common mistakes
Using v = u + at when acceleration varies
Confusing average velocity with average speed
Keywords
kinematics
displacement
velocity
acceleration
velocity time graph
slope
area
straight line motion