A 5 kg block rests on a horizontal surface. The static frictional coefficient is 0.55 and the kinetic frictional coefficient is 0.45. Calculate the static and kinetic frictional forces.

The mass of the block is $m = 5 \text{ kg}$.
The static frictional coefficient is $\mu_s = 0.55$.
The kinetic frictional coefficient is $\mu_k = 0.45$.
Assume the acceleration due to gravity $g = 9.8 \text{ m/s}^2$.

For a block on a horizontal surface, the normal force is equal to its weight.
Weight $W = m \times g$

Therefore, the normal force is $F_N = 49 \text{ N}$.

The formula for static friction is $F_s = \mu_s F_N$.
Substitute the values:

The formula for kinetic friction is $F_k = \mu_k F_N$.
Substitute the values:

The answers are:

4.1 Static frictional force: $\boxed{\text{26.95 N}}$

4.2 Kinetic frictional force: $\boxed{\text{22.05 N}}$