Question

Which free-body diagram shows an object that will accelerate?

A. diagram A
B. diagram B
C. diagram C
D. diagram D​

Answer 1

The free-body diagram that shows an object that will accelerate are options C. diagram C and D. diagram D​

From the image., in option c, the force pushing the object is greater than the force opposing it, so there will be movement.

For option d, the force pushing is less that the force opposing it so, there will be movement to the opposite direction

So, According to Newton's second law of motion, an object will accelerate when the net force acting on it is non-zero. Therefore, to determine which free-body diagram shows an object that will accelerate, one need to see the net force for each diagram.

Answer 2

Answer: Diagram C

Step-by-step explanation:

When a body is under the influence of 2 or more forces, the effect of all forces may be replaced by a unique force (resulting force), with the same result as all original forces.

In case you have different forces with the same direction but different sense, all forces may be substituted by one resulting force, though the module of this resulting force will be equal to the absolute value of the substraction of the modules of the individual forces

For case C, you should check: 8 N (force with right sense) + 4 N (force with right sense) - 4 N (force with left sense) would give us a resulting force of 8 N (with right sense), which will accelerate the body to the right