Motion Exemplar — Class 9 Science NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 9 Science chapter "Motion Exemplar" — 5 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 9 Science chapter "Motion Exemplar" — 5 important questions with detailed answers for CBSE board exam prep…
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NCERT Solutions for Class 9 Science — Motion Exemplar. Step-by-step answers to all 5 textbook questions from this chapter, written for CBSE board preparation and free to use.
Motion Exemplar — All 5 Questions Solved
Q1. A car accelerates uniformly from 10 m/s to 30 m/s in 5 seconds. Calculate acceleration and distance covered.
u = 10 m/s, v = 30 m/s, t = 5 s. Acceleration a = (v - u)/t = (30 - 10)/5 = 4 m/s². Distance s = ut + (1/2)at² = 10(5) + (1/2)(4)(25) = 50 + 50 = 100 m.
Q2. Define velocity and speed. A boy walks 4 km in 2 hours. Calculate both.
Speed is distance/time = 4/2 = 2 km/h. Velocity is displacement/time. If displacement is also 4 km in same direction, velocity = 2 km/h in that direction. If he returns to origin, displacement = 0, velocity = 0.
Q3. An object is thrown upward with initial velocity 20 m/s. Find maximum height and time to return (g = 10 m/s²).
At max height, v = 0. Using v² = u² - 2gh: 0 = 400 - 2(10)h. So h = 20 m. Time to max height: v = u - gt: 0 = 20 - 10t, so t = 2 s. Total time to return = 2 × 2 = 4 s.
Q4. A ball is dropped from height 45 m. How long does it take to reach ground? (g = 10 m/s²)
Using s = (1/2)gt²: 45 = (1/2)(10)t². So 45 = 5t², giving t² = 9, thus t = 3 s.
Q5. State Newton's first law and explain with example.
Newton's first law: an object at rest stays at rest and object in motion continues with constant velocity unless acted upon by external force. Example: passengers jerk forward when bus suddenly stops because body tends to continue forward motion due to inertia.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.