A block, of mass 8 kg, is placed on a rough horizontal surface - NSC Physical Sciences - Question 2 - 2018 - Paper 1

The free-body diagram for the 8 kg block should include:

1. The weight of the block acting downwards (W = mg, where m = 8 kg and g = 9.81 m/s²).
2. The normal force acting upwards.
3. The tension in the string acting at an angle of 15° above the horizontal.
4. The frictional force acting opposite to the direction of motion.

The system is not in equilibrium because the 8 kg block is experiencing a net acceleration of 1.32 m/s². This acceleration indicates that there is a resultant force acting on the block, and thus the forces are unbalanced.

To calculate the tension in the string, we can analyze the forces acting on the 2 kg block:

1. The net force acting on the block is given by: $F_{net} = ma \rightarrow F_{net} = 2 kg \times 1.32 m/s² = 2.64 N$

2. The tension in the string can also be found using: $T = mg - F_{net} \rightarrow T = (2 kg \times 9.81 m/s²) - 2.64 N = 19.62 N - 2.64 N = 16.98 N$

We calculate the kinetic frictional force ( f_k = ext{Friction Coefficient} \times N

To find the normal force (N), we have: $N = mg = 8 kg \times 9.81 m/s² = 78.48 N$

If we assume the coefficient of kinetic friction is known (( , \mu_k )), then:

$f_k = \mu_k \times N = \mu_k \times 78.48 N$

Based on the question’s data, if ( , \mu_k ) is calculated from earlier results, use that specific value, or denote the method to find it.

The kinetic frictional force changes as the 8 kg block moves from B to C because the nature of the surfaces in contact may change. Different materials have varying coefficients of friction, which will result in a change in the frictional force experienced by the block as it transitions from one surface to another.

YES. The kinetic frictional force will change because it depends on the properties of the surfaces in contact. If the horizontal surface the 8 kg block is moving on is changed to a different material, the coefficient of kinetic friction will likely differ, resulting in a different kinetic frictional force.