Question

A block of mass 3 kg slides along a horizontal surface that has negligible friction except for one section, as shown above. The block arrives at the rough section with a speed of 5 m/s and leaves it 0.5 s later with a speed of 3 m/s.

Answer 1

Complete Question

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Answer:

The value  is $F_f = 3 * -4$

Explanation:

From the question we are told that  

  The mass of the block is  $m = 3 \ kg$

  The initial speed of the block before entering the rough section is $u = 5 \ m/s$

  The time taken is  t = 0.5 s

   The  speed with which the block leaves the rough section is  $v = 3 \ m/s$

Generally from kinematic equation

      $v = u + at$

=>   $a = \frac{v - u }{t}$

=>   $a = \frac{3 - 5 }{0.5}$

=>   $a = - 4$

Generally the magnitude of the average frictional  force is mathematically represented as

      $F_f = m * a$

=>  $F_f = 3 * -4$

=>    $F_f = -12 \ N$

The negative sign show that the force is acting in the opposite direction to the direction of motion of the block

Answer 2

The frictional force between the block and the horizontal surface is 12.1 N.

The given parameters;

• mass of the block, m = 3 kg
• initial speed of block, u = 5 m/s
• time of motion, t = 0.5 s
• final speed, v = 3 m/s

The acceleration of the block is calculated as follows;

$a = \frac{\Delta v}{t} \\\\a = \frac{5- 3}{0.5} \\\\a = 4 \ m/s^2$

The coefficient of friction between the block and the horizontal surface is calculated as;

$\mu_k = \frac{a}{g} \\\\\mu_k = \frac{4}{9.8} \\\\\mu_k = 0.41$

The frictional force between the block and the horizontal surface is calculated as follows;

$F_f = \mu_k F_n\\\\F_f = \mu_k mg\\\\F_f = 0.41 \times 3 \times 9.8\\\\F_f = 12 .1 \ N$

Thus, the frictional force between the block and the horizontal surface is 12.1 N.

"Your question is not complete, it seems to be missing the following information;"

A block of mass 3 kg slides along a horizontal surface that has negligible friction except for one section, as shown above. The block arrives at the rough section with a speed of 5 m/s and leaves it 0.5 s later with a speed of 3 m/s. What is the magnitude of the average frictional force exerted on the block by the rough section of the surface?

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