Contact Forces Problem

A crate resting on a floor has weight, normal, friction, and Force forces.  The normal and weight forces are balanced.  The friction and Force forces aren't balanced because the object is moving forward therefore there is a positive force to the right.  Friction is negative because it takes away force by slowing it down.

To find the weight force, mass multiplied by acceleration is enforced (ma=W).  The weight force is negative because acceleration is negative (-9.8m/s2).

Normal force and weight force are balanced, so the normal will equal the weight force except a positive number.  The normal and weight forces added together should equal zero.

Next, the frictional force should be calculated using the friction equals mu multiplied by Normal equation. N signifies normal force, while M represents the coefficient of friction.  The coefficient of friction is given (0.15) and is mulitplied by the Normal just calculated (490N) to find friction (73.5N).

Finally to calculate acceleration, the equation Net Force equals mass multiplied by acceleration should be used.  EF signifies net force which will be Force subtracted by friction.  The mass is given in the problem (50kg).  To solve for acceleration, subtract the friction force from the Force.  Then, divide that number by the mass to find acceleration.