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Describe what is meant by significant figures.
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A large ball 2 m in radius is made up of a rope of square cross-section with edge length 4 mm. Neglecting the air gaps in the ball, what is the total length of the rope to the nearest order of magnitude?
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Solve the numerical example.
Nuclear radius R has a dependence on the mass number (A) as R =1.3 × 10-16 A1/3 m. For a nucleus of mass number A = 125, obtain the order of magnitude of R expressed in the meter.
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Solve the numerical example.
Write down the number of significant figures in the following: 0.003 m2, 0.1250 gm cm-2, 6.4 x 106 m, 1.6 x 10-19 C, 9.1 x 10-31 kg.
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Solve the numerical example.
The diameter of a sphere is 2.14 cm. Calculate the volume of the sphere to the correct number of significant figures.
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Answer in one sentence.
Define friction.
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Answer in one sentence.
Why force of static friction is known as ‘self-adjusting force’?
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Answer in one sentence.
Name two factors on which the coefficient of friction depends.
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State any four methods to reduce friction.
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Answer in short.
What is rolling friction? How does it arise?
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Answer in short.
Explain how lubricants help in reducing friction.
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Answer in short.
State the laws of static friction.
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Answer in short.
State the laws of kinetic friction.
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Answer in short.
State advantages of friction.
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State disadvantages of friction.
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Long answer type question.
Define coefficient of static friction and coefficient of kinetic friction. Give the necessary formula for each.
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Calculate the coefficient of static friction for an object of mass 50 kg placed on horizontal table pulled by attaching a spring balance. The force is increased gradually it is observed that the object just moves when spring balance shows 50 N.
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Answer the following.
A block of mass 37 kg rests on a rough horizontal plane having coefficient of static friction 0.3. Find out the least force required to just move the block horizontally.
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A body of mass 37 kg rests on a rough horizontal surface. The minimum horizontal force required to just start the motion is 68.5 N. In order to keep the body moving with constant velocity, a force of 43 N is needed. What is the value of coefficient of static friction?
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The internal resistance of a cell of emf 2 V is 0.1 Ω it is connected to a resistance of 0.9 Ω. The voltage across the cell will be ______.
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