Question

if f = 210 n, the σf acting on the object is.
if f < 210 n, the σf acting on the object is.

Explanation:

Step1: Determine the direction of forces

Assume the right - hand direction is positive. The force of \(300N\) is to the right, and the forces of \(90N\) and \(F\) are to the left.

Step2: Calculate the net force when \(F = 210N\)

The sum of forces \(\sum\vec{F}=300-(90 + F)\). Substitute \(F = 210N\) into the formula: \(\sum\vec{F}=300-(90 + 210)=300 - 300=0N\)

Step3: Calculate the net force when \(F<210N\)

Let \(F = 210 - k\) (\(k>0\)). Then \(\sum\vec{F}=300-(90+(210 - k))=300-(300 - k)=k>0\). Since \(k>0\), the net force is to the right.

Answer:

When \(F = 210N\), the sum of forces is \(0\). When \(F<210N\), the sum of forces is to the right.