A horizontal force is applied to a 10kg block on a surface with a coefficient of friction of 0.4. What force must be applied to just exceed the friction?

To determine the force that must be applied to just exceed the friction acting on the block, we can calculate the force of friction using the formula:

Frictional Force (f) = μ * N

where:

• μ is the coefficient of friction,

• N is the normal force.

For a horizontal surface, the normal force (N) is equal to the weight of the block, which can be calculated as:

N = mass * gravitational acceleration

In this case, the mass of the block is 10 kg, and the gravitational acceleration is approximately 9.8 m/s². Thus,

N = 10 kg * 9.8 m/s² = 98 N.

Now, we can calculate the frictional force using the coefficient of friction of 0.4:

f = 0.4 * 98 N = 39.2 N.

This value means that a force greater than 39.2 N is required to overcome the friction and cause the block to start moving. Therefore, the correct answer is 39.2 N, as this is the minimum force that must be applied to exceed the friction acting on the block.