A block of mass 4 kg rests on a frictionless horizontal surface, what horizontal force is required to accelerate the block at 5 m/s^2 ?

20N

Explanation:

Given parameters:

Mass of the block  = 4kg

Acceleration  = 5m/s²

Unknown:

Horizontal force needed to accelerate the block  = ?

Solution:

According to Newton's second law of motion;

     Force  = mass x acceleration

Now insert the parameters and solve;

        Horizontal force  = 4 x 5  = 20N

your answer is c! hope this : )

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