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Dynamics
6 Class 9 Physics questions with answers and explanations.
Printable worksheet with answer key
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Newton's first law of motion is also called the law of:
- 1 Gravitation
- 2 Acceleration
- 3 Momentum transfer
- 4 Inertia
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Correct answer: Inertia
A body stays at rest or in uniform motion unless a net force acts on it. This property is inertia.
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What force is needed to give a mass of 5 kg an acceleration of 3 m/s2?
- 1 8 N
- 2 1.7 N
- 3 15 N
- 4 2 N
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What is the SI unit of momentum?
- 1 kg m/s2
- 2 N
- 3 J
- 4 kg m/s
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Correct answer: kg m/s
Momentum = mass x velocity, so its unit is kg m/s.
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When a gun fires a bullet, the gun recoils. This is explained by:
- 1 Newton's second law
- 2 Newton's first law
- 3 Newton's third law
- 4 Law of gravitation
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Correct answer: Newton's third law
The force on the bullet has an equal and opposite reaction force on the gun.
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What is the weight of a 10 kg mass on Earth? (g = 10 m/s2)
- 1 10 N
- 2 1 N
- 3 100 N
- 4 0.1 N
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The force that opposes the motion of one surface over another is called:
- 1 Thrust
- 2 Friction
- 3 Tension
- 4 Gravity
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Correct answer: Friction
Friction acts between surfaces in contact and opposes relative motion.