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Important Questions

Work, Energy, and Simple Machines — Important Questions

CBSE · Class 9 · Science

80 important questions from Work, Energy, and Simple Machines for CBSE Class 9 Science, with answers. Part of the CBSE Class 9 Science syllabus.

80 questions80 flashcards8 formulas & key relations5 concepts

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A line graph showing distance on the Y-axis and time on the X-axis, depicting a straight line passing through the origin, representing uniform speed. Includes labels for calculating speed from the slo
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80 Questions·
multiple choicemultiple correcttrue falsefill in blanksnumerical

Important Questions from Work, Energy, and Simple Machines

1multiple choice
3 marks

A car of mass 1000 kg starts from rest and reaches 72 km h^-1 in 10 s. What is the power of the engine?

Show answer

20,000 W

From the previous calculation, work done is 200,000 J. Power = W/t = 200,000/10 = 20,000 W.

2multiple choice
3 marks

A cricket ball of mass 0.2 kg is bowled at 154.8 km h^-1. What is its kinetic energy?

Show answer

184.9 J

Convert speed: 154.8 km h^-1 = 43 m s^-1. Then K = 1/2 mv^2 = 1/2 × 0.2 × 43^2 = 0.1 × 1849 = 184.9 J.

3multiple choice
3 marks

A cricket ball of mass 0.2 kg is thrown so that it reaches a height of 10 m. Taking g = 10 m s^-2, what is its gravitational potential energy at the top?

Show answer

20 J

Use U = mgh = 0.2 × 10 × 10 = 20 J.

4multiple choice
3 marks

A child slides down from a height of h and reaches the bottom with speed v, neglecting friction. If h = 5 m and g = 10 m s^-2, what is the speed at the bottom?

Show answer

10 m s^-1

Use conservation of mechanical energy: mgh = 1/2 mv^2. Mass cancels, so v = sqrt(2gh) = sqrt(2 × 10 × 5) = sqrt(100) = 10 m s^-1.

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Frequently Asked Questions

What are the important topics in Work, Energy, and Simple Machines for CBSE Class 9 Science?
Key topics in Work, Energy, and Simple Machines include Work Done by a Constant Force, Work-Energy Theorem and Kinetic Energy, Potential Energy and Mechanical Energy, Power. Study these first, then practise questions on each for Class 9 exams.
How many important questions are there in Work, Energy, and Simple Machines?
Super Tutor has 80 practice questions for Work, Energy, and Simple Machines, including multiple choice, multiple correct, true false, fill in blanks, numerical questions. A sample with answers is on this page.

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Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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