Question

A 5 kg block is pulled across a table by a horizontal force of 40 N with a frictional force of 8 N opposing the motion. Calculate the acceleration of the object.

Answer 1

Answer:

a = 6.4 [m/s²]

Explanation:

To solve this problem we must use Newton's second law, which tells us that the sum of forces on a body is equal to the product of mass by acceleration. In this way, we have the following equation.

∑F = m*a

where:

∑F = sum of forces (horizontal force = 40 [N] and friction force = 8 [N])

m = mass of the block = 5 [kg]

a = acceleration [m/s²]

Now replacing:

$40-8=5*a\\32 = 5*a\\a=6.4[m/s^{2} ]$

Note: the sign of the friction force is negative since this force is acting against the movement of the block.