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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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Solve the following problem.
A battery after a long use has an emf 24 V and an internal resistance 380 Ω. Calculate the maximum current drawn from the battery? Can this battery drive starting motor of car?
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Solve the following problem.
A battery of emf 12 V and internal resistance 3 Ω is connected to a resistor. If the current in the circuit is 0.5 A,
- Calculate resistance of resistor.
- Calculate terminal voltage of the battery when the circuit is closed.
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Answer the following question.
Describe what is meant by order of magnitude.
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Justify the statement, “Work and energy are the two sides of a coin.”
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Answer the following question.
From the terrace of a building of height H, you dropped a ball of mass m. It reached the ground with speed v. Is the relation mgh = `1/2"mv"^2` applicable exactly? If not, how can you account for the difference? Will the ball bounce to the same height from where it was dropped?
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100 cells each of emf 5 V and internal resistance 1 Ω are to be arranged so as to produce maximum current in a 25 Ω resistance. Each row contains equal number of cells. The number of rows should be ______.
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Choose the correct alternative.
Five dry cells each of voltage 1.5 V are connected as shown in the diagram
What is the overall voltage with this arrangement?
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Give reason/short answer.
In the given circuit diagram two resistors are connected to a 5V supply.
Calculate potential difference across the 8Ω resistor.
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