Final answer:
The friction force acting on the block is 20N upwards.
Step-by-step explanation:
The friction force acting on the block is 20N upwards.
To find the friction force, we need to calculate the normal force exerted on the block by the surface. The normal force is equal in magnitude and opposite in direction to the gravitational force acting on the block.
The gravitational force can be calculated using the formula F = mg, where m is the mass of the block and g is the acceleration due to gravity (9.8 m/s^2).
In this case, the mass of the block is 3 kg, so the gravitational force is F = (3 kg)(9.8 m/s^2) = 29.4 N.
Since the coefficient of friction is 0.25, the friction force can be calculated as the product of the coefficient of friction and the normal force.
The normal force is equal to the gravitational force, so the friction force is F_friction = (0.25)(29.4 N) = 7.35 N.
However, the friction force always acts opposite to the direction of motion, so the friction force is actually 7.35 N upwards