A7LAM CSCA ACADEMYCSCA Academy / Physics / Mechanics
CSCA Physics · Lesson 1 of 16Motion
Mouvement · الحركة
▶ Watch the video lesson (A7LAM students)
Kinematics describes motion with position, velocity and acceleration. For constant acceleration, four equations solve almost every problem.
Key ideas
- Average speed = distance / time. Velocity has a direction, speed does not.
- Acceleration a = change in velocity / time.
- With constant acceleration: v = v₀ + at and s = v₀t + ½at².
- Free fall near Earth: a = g ≈ 9.8 m/s² downward (often rounded to 10).
Formulas to know
- v = v₀ + at
- s = v₀t + ½at²
- v² = v₀² + 2as
Worked example
A car starts from rest and accelerates at 2 m/s² for 5 s. How far does it travel?
- v₀ = 0, a = 2 m/s², t = 5 s.
- s = ½ · 2 · 5².
Answer: s = 25 m
Practice questions
1. A runner covers 100 m in 12.5 s. Average speed?
6 m/s · 8 m/s ✓ · 10 m/s · 12.5 m/s
100 / 12.5 = 8 m/s.
2. A ball is dropped from rest (g = 10 m/s²). Its speed after 3 s?
10 m/s · 30 m/s ✓ · 45 m/s · 90 m/s
v = gt = 10 × 3 = 30 m/s.
3. A car slows from 20 m/s to 0 in 4 s. Its acceleration?
5 m/s² · −5 m/s² ✓ · −80 m/s² · 80 m/s²
a = (0 − 20)/4 = −5 m/s² (it decelerates).