What is the net external force of an object?

How do you determine the net force on an object?

Decide which direction is positive motion.

Motion is the opposite direction is negative

The forces must in a straight line!!

Add all the forces in straight line acting on the object.

Example

To the right is positive

A 5 N force pushes a 10 Kg object to the right.

A 2 N force pushes the same 10 Kg object to the left.

The 5 N forces is positive and the 2N force is negative

Net force = +5 N - 2 N = + 3 N

To determine the acceleration use Newton's 2nd law of motion

F = Mass * acceleration

+ 3 N = 10 Kg * a

a = 10 Kg ÷ + 3 N

a = +3 ⅓ m/s^2

The positive sign means the object is accelerating to the right!!

If the forces are not linear, you must use vectors, but the net force in any direction is still the sum of the vectors in that direction.