Net Force Physics Example 3

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Example 3

medium
A 4 kg4 \text{ kg} object experiences forces of 20 N20 \text{ N} forward and 8 N8 \text{ N} backward. What is the net force and resulting acceleration?

Solution

  1. 1
    Define forward as positive. The driving force is +20 N+20 \text{ N} and friction is −8 N-8 \text{ N}.
  2. 2
    Calculate the net force: Fnet=20−8=12 N forwardF_{\text{net}} = 20 - 8 = 12 \text{ N forward}
  3. 3
    Apply Newton's second law to find acceleration: a=Fnetm=124=3 m/s2a = \frac{F_{\text{net}}}{m} = \frac{12}{4} = 3 \text{ m/s}^2

Answer

Fnet=12 N,a=3 m/s2F_{\text{net}} = 12 \text{ N}, \quad a = 3 \text{ m/s}^2
The net force determines the acceleration. Even when multiple forces act, only the net force matters for determining motion changes.

About Net Force

The single resultant force obtained by vector addition of all individual forces acting on an object, which alone determines the object's acceleration according to Newton's.

Learn more about Net Force →

More Net Force Examples

Example 1 easy

Three forces act on an object: [formula] right, [formula] left, and [formula] left. What is the net

Example 2 medium

Two perpendicular forces act on an object: [formula] east and [formula] north. What is the magnitude

Example 4 easy

A [formula] sled accelerates east at [formula]. What is the net force on the sled?

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