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A man wants to slide down a block of mas...

A man wants to slide down a block of mass `m` which is kept on a fixed inclined plane of inclination `30^(@)` as shown in the figure .Initially the block is not sliding .
To just start sliding the man pushed the block down the inclined with a force `F`. Now , the block starts accelerating. To move it downwards with conatant speed the man starts pulling the block with same force. Surface are such that ratio of maximum static friction to kinetic friction is `2` Now, answer the following questions.

If the man wants to move the block up the inclined , what minimum force is required to start the motion?

A

`(2)/(3) mg`

B

`(mg)/(2)`

C

`(7 mg)/(6)`

D

`(5 mg)/(6)`

Text Solution

Verified by Experts

The correct Answer is:
C
`F' = mg sin theta + mu_(s) mg cos theta`
`= (mg)/(2) + (4)/(3 sqrt3) mg ((sqrt3)/(2))`
`= (7 mg)/(6)`
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A man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in the figure .Initially the block is not sliding . To just start sliding the man pushed the block down the inclined with a force F . Now , the block starts accelerating. To move it downwards with conatant speed the man starts pulling the block with same force. Surface are such that ratio of maximum static friction to kinetic friction is 2 Now, answer the following questions. What is the value of mu _(s) , the coefficient of static friction?

When we apply a horizontal force on a body kept on horizontal floor, a horizontal force starts opposing the net applied force. This force is called frictional force and is always tangential to the contact surface. Frictional force on a moving body is called kinetic friction which is directly proportional to the normal force (f_(k)=mu_(k)N) where mu_(k) is a constant depending upon the surfaces and is called the coefficient of kinetic friction. Frictional force on a static body is called static friction. Maximum value of static friction force is (f_(s) le mu_(s)N) , where mu_(s) is coefficient of static friction. Now a man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in figure initially, the block is not sliding. To just start sliding the man pushes the block down the inclined with a force F. Now the block starts accelerating. To move it downwards with constant speed, the man starts pulling the block with same force. Surfaces are such that ratio of maximum static friction to kinetic friction is 2. Now, answer the following questions. If man continues pushing the block by force F, its acceleration would be

Knowledge Check

  • A man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in the figure .Initially the block is not sliding . To just start sliding the man pushed the block down the inclined with a force F . Now , the block starts accelerating. To move it downwards with conatant speed the man starts pulling the block with same force. Surface are such that ratio of maximum static friction to kinetic friction is 2 Now, answer the following questions. What is the value of F ?

    A
    `(mg)/(4)`
    B
    `(mg)/(6)`
    C
    `(mg sqrt3)/(4)`
    D
    `(mg)/(2 sqrt3)`

  • A man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in the figure .Initially the block is not sliding . To just start sliding the man pushed the block down the inclined with a force F . Now , the block starts accelerating. To move it downwards with conatant speed the man starts pulling the block with same force. Surface are such that ratio of maximum static friction to kinetic friction is 2 Now, answer the following questions. If the man continues pushing the block by force F its acceleration would be

    A
    `(g)/(6)`
    B
    `(g)/(4)`
    C
    `(g)/(2)`
    D
    `(g)/(3)`

  • A man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in the figure .Initially the block is not sliding . To just start sliding the man pushed the block down the inclined with a force F . Now , the block starts accelerating. To move it downwards with conatant speed the man starts pulling the block with same force. Surface are such that ratio of maximum static friction to kinetic friction is 2 Now, answer the following questions. What minimum force is required to move it up the incline with constant speed?

    A
    `(2)/(3) mg`
    B
    `(mg)/(2)`
    C
    `(7 mg)/(6)`
    D
    `(5 mg)/(6)`

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    When we apply a horizontal force on a body kept on horizontal floor, a horizontal force starts opposing the net applied force. This force is called frictional force and is always tangential to the contact surface. Frictional force on a moving body is called kinetic friction which is directly proportional to the normal force (f_(k)=mu_(k)N) where mu_(k) is a constant depending upon the surfaces and is called the coefficient of kinetic friction. Frictional force on a static body is called static friction. Maximum value of static friction force is (f_(s) le mu_(s)N) , where mu_(s) is coefficient of static friction. Now a man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in figure initially, the block is not sliding. To just start sliding the man pushes the block down the inclined with a force F. Now the block starts accelerating. To move it downwards with constant speed, the man starts pulling the block with same force. Surfaces are such that ratio of maximum static friction to kinetic friction is 2. Now, answer the following questions. What is the value of F?

    When we apply a horizontal force on a body kept on horizontal floor, a horizontal force starts opposing the net applied force. This force is called frictional force and is always tangential to the contact surface. Frictional force on a moving body is called kinetic friction which is directly proportional to the normal force (f_(k)=mu_(k)N) where mu_(k) is a constant depending upon the surfaces and is called the coefficient of kinetic friction. Frictional force on a static body is called static friction. Maximum value of static friction force is (f_(s) le mu_(s)N) , where mu_(s) is coefficient of static friction. Now a man wants to slide down a block of mass m which is kept on a fixed inclined plane of inclination 30^(@) as shown in figure initially, the block is not sliding. To just start sliding the man pushes the block down the inclined with a force F. Now the block starts accelerating. To move it downwards with constant speed, the man starts pulling the block with same force. Surfaces are such that ratio of maximum static friction to kinetic friction is 2. Now, answer the following questions. What is the value of mu_(s) ?

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