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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Key Questions Covered:
- A car accelerates uniformly from 10 m/s to 30 m/s in 5 seconds. Calculate acc…
- Define velocity and speed. A boy walks 4 km in 2 hours. Calculate both.
- An object is thrown upward with initial velocity 20 m/s. Find maximum height …
- A ball is dropped from height 45 m. How long does it take to reach ground? (g…
- State Newton's first law and explain with example.
Solutions Summary:
| Question | Status |
|---|---|
| A car accelerates uniformly from 10 m/s to 30 m/s in 5 se… | ✓ Solved |
| Define velocity and speed. A boy walks 4 km in 2 hours. C… | ✓ Solved |
| An object is thrown upward with initial velocity 20 m/s. … | ✓ Solved |
| A ball is dropped from height 45 m. How long does it take… | ✓ Solved |
| State Newton's first law and explain with example. | ✓ Solved |
Showing 5 of 5 questions
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.
Showing 5 of 5 questions. Visit the full page for complete solutions.
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