Q1.AccelerationEasy · 1m
Define acceleration and give its SI unit.
Answer: Acceleration is the rate of change of velocity; its SI unit is m/s².
Class 9 · Science · Important Questions
Motion — Important Questions
Q2.Distance & DisplacementEasy · 2m
Differentiate between distance and displacement.
Answer: Distance is the total path length covered (a scalar, always ≥ 0); displacement is the shortest distance between the initial and final positions (a vector, and can be zero).
Q3.Speed & VelocityEasy · 2m
Differentiate between speed and velocity.
Answer: Speed is distance per unit time (a scalar); velocity is displacement per unit time (a vector, having direction).
Q4.Equations of MotionMedium · 3m
Write the three equations of uniformly accelerated motion.
Answer: v = u + at; s = ut + ½at²; v² = u² + 2as.
Q5.NumericalMedium · 3m
A car starting from rest reaches 20 m/s in 5 s. Find its acceleration and the distance covered.
Answer: a = (20 − 0)/5 = 4 m/s²; s = ut + ½at² = 0 + ½ × 4 × 5² = 50 m.
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