Question icon
Grade upto college level Electric Current

A block P of mass m is placed on a horizontal frictionless plane.

A second block of same mass m is placed on it and is connected to
a spring of spring constant k, the two blocks are pulled by distance
A. Block Q oscillates without slipping. What is the maximum
value of frictional force between the two blocks

Profile image of Shane Macguire
12 Years agoGrade upto college level
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1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

To analyze the scenario you've described, we need to consider the forces acting on both blocks and how they interact with each other. Since block P is on a frictionless surface and block Q is on top of it, the frictional force between the two blocks is crucial for understanding their motion, especially when block Q is oscillating due to the spring.

Understanding the System

We have two blocks, both with mass m. Block P is on a frictionless horizontal plane, while block Q is resting on top of block P and is connected to a spring with spring constant k. When the blocks are pulled by a distance A, they will experience oscillatory motion due to the spring's restoring force.

Forces Acting on Block Q

When block Q is displaced by distance A, it will experience a restoring force from the spring, given by Hooke's Law:

  • Restoring Force (F) = -k * x, where x is the displacement from the equilibrium position.

In this case, when block Q is pulled by distance A, the force exerted by the spring on block Q will be:

  • F = -k * A

Frictional Force Between the Blocks

The frictional force between the two blocks is what allows block Q to oscillate without slipping off block P. The maximum static frictional force can be calculated using the formula:

  • F_friction(max) = μ_s * N

Here, μ_s is the coefficient of static friction between the two blocks, and N is the normal force acting on block Q, which is equal to the weight of block Q:

  • N = m * g, where g is the acceleration due to gravity.

Thus, the maximum static frictional force becomes:

  • F_friction(max) = μ_s * m * g

Condition for Oscillation Without Slipping

For block Q to oscillate without slipping, the frictional force must be able to counteract the spring force. Therefore, we set the maximum frictional force equal to the spring force:

  • μ_s * m * g ≥ k * A

This inequality tells us that for block Q to remain on top of block P without slipping, the static friction must be sufficient to counteract the force exerted by the spring when block Q is displaced by distance A.

Conclusion

In summary, the maximum value of the frictional force between the two blocks is determined by the coefficient of static friction and the weight of block Q. It can be expressed as:

  • F_friction(max) = μ_s * m * g

This frictional force plays a critical role in ensuring that block Q can oscillate without slipping off block P, as long as the spring force does not exceed this maximum frictional force. Understanding these dynamics helps us analyze similar systems in physics, where friction and oscillation are involved.