A 25.2 kg block of wood is pulled across a floor at a constant 9.74 m/s with a constant 62.7 N force. The bottom of the box has a surface area of 65.1 cm2. If the block was put on its side (which has twice the surface area of the bottom) and pulled with the same force at the same constant speed, what is the friction force between the box and the floor?
67.2 N. Think out why.
To find the friction force between the block and the floor, you need to use the equation for frictional force:
Frictional force = coefficient of friction * Normal force
The coefficient of friction depends on the nature of the surfaces in contact. Given that the block is being pulled at a constant speed, we can assume that the frictional force and the applied force are equal in magnitude but opposite in direction.
First, let's find the normal force acting on the block. When the box is on its bottom, the entire weight of the block acts downward, perpendicular to the surface. Therefore, the normal force is equal to the weight of the block.
Normal force = mass * acceleration due to gravity
mass = 25.2 kg
acceleration due to gravity = 9.8 m/s^2
Normal force = 25.2 kg * 9.8 m/s^2
Now, let's calculate the frictional force when the block is on its bottom:
Frictional force (bottom) = coefficient of friction * Normal force (bottom)
Next, let's find the normal force when the block is on its side. Since the weight is spread over twice the surface area, the normal force would be half of the weight for the same pressure.
Normal force (side) = (1/2) * mass * acceleration due to gravity
Finally, calculate the frictional force when the block is on its side using the equation mentioned earlier:
Frictional force (side) = coefficient of friction * Normal force (side)
Now compare the frictional forces between the block and the floor in both cases.