Question icon
Grade 12Mechanics

a block of mass 5 kg rests on a horizontal floor when a constant horizontal force is applied on the block for a time interval 5 second the block slides on a floor India distance 5m under the action of the force and after the removal of force it for the slides a distance 1 metre before coming to stop acceleration due to gravity is 10 M per second magnitude of the applied force is

Profile image of Saidamma G
7 Years agoGrade 12
Answers icon

1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

To determine the magnitude of the applied force on the block, we can break down the problem into two main phases: the sliding phase while the force is applied and the sliding phase after the force is removed. Let's analyze each phase step by step.

Phase 1: Force Applied

During the first phase, a constant horizontal force is applied to the block for 5 seconds, causing it to slide a distance of 5 meters. We can use the equations of motion to find the acceleration of the block.

Using the Equation of Motion

We can use the equation:

  • s = ut + (1/2)at²

Where:

  • s = distance (5 m)
  • u = initial velocity (0 m/s, since it starts from rest)
  • a = acceleration (unknown)
  • t = time (5 s)

Substituting the known values into the equation:

  • 5 = 0 * 5 + (1/2)a(5²)

This simplifies to:

  • 5 = (1/2)a(25)

From here, we can solve for acceleration:

  • 5 = 12.5a
  • a = 5 / 12.5 = 0.4 m/s²

Phase 2: Force Removed

After the force is removed, the block continues to slide for an additional distance of 1 meter before coming to a stop. We need to find the deceleration (negative acceleration) during this phase.

Finding Deceleration

We can use the same equation of motion, but this time we know the final velocity will be 0 m/s when the block stops:

  • s = ut + (1/2)at²

Here:

  • s = 1 m
  • u = final velocity from the first phase (which we need to calculate)
  • a = deceleration (unknown)
  • t = time (unknown)

First, we need to find the final velocity (u) at the end of the first phase:

  • v = u + at

Substituting the known values:

  • v = 0 + (0.4)(5) = 2 m/s

Now, we can use this final velocity as the initial velocity for the second phase:

  • 1 = (2)t + (1/2)(-a)t²

We need to express time in terms of acceleration. We can use another equation:

  • v² = u² + 2as

Setting v = 0, u = 2 m/s, and s = 1 m:

  • 0 = (2)² + 2(-a)(1)

This simplifies to:

  • 0 = 4 - 2a
  • 2a = 4
  • a = 2 m/s²

Calculating the Applied Force

Now that we have the acceleration while the force was applied (0.4 m/s²), we can find the net force acting on the block using Newton's second law:

  • F_net = ma

Where:

  • m = mass of the block (5 kg)
  • a = acceleration (0.4 m/s²)

Calculating the net force:

  • F_net = 5 kg * 0.4 m/s² = 2 N

However, this is the net force. We also need to account for the force of friction acting against the motion. The force of friction can be calculated using:

  • F_friction = μN

Where:

  • μ = coefficient of friction (unknown)
  • N = normal force (which equals mg = 5 kg * 10 m/s² = 50 N)

Assuming the block is sliding on a surface with a coefficient of friction (let's say μ = 0.2 for this example), we can calculate:

  • F_friction = 0.2 * 50 N = 10 N

Now, the total applied force (F_applied) can be found by adding the net force and the force of friction:

  • F_applied = F_net + F_friction
  • F_applied = 2 N + 10 N = 12 N

Thus, the magnitude of the applied force is 12 N, assuming a coefficient of friction of 0.2. If the coefficient of friction is different, you would need to adjust the calculations accordingly.