Net force — Science definition
Defined in 2 courses:
- The overall force on an object after combining all individual forces, accounting for direction. (Physical Science: Matter, Forces & Energy)
- Directional sum of forces on one object. (Physical Science: Matter, Forces & Energy)
Where it is taught
- Balanced & Unbalanced Forces — Forces, Physical Science: Matter, Forces & Energy, Grade 8
- Interaction Pairs & Force Diagrams — Forces, Physical Science: Matter, Forces & Energy, Grade 8
In use
What actually determines how an object moves isn't any one of those forces alone, but the net force — the single overall force you get after combining all of them, carefully accounting for direction.
Balanced & Unbalanced Forces
Questions using net force
Problem 1
A rope pulls a sled forward with 60 N while friction pulls back with 20 N. What is the net force?
Answer and explanation
40 N
Net force = 60 − 20 = 40 N (forward).
Problem 2
If the net force on an object is zero, the object…
- must be at rest
- is either at rest or moving at constant velocity
- must be accelerating
- must be speeding up
Answer and explanation
is either at rest or moving at constant velocity
A zero net force means no change in motion — the object could be still, or cruising at a steady velocity.
Problem 3
Two tug-of-war teams pull with 500 N and 470 N in opposite directions. Find the net force.
Answer and explanation
30 N
Net force = 500 − 470 = 30 N, in the direction of the stronger team.
Problem 4
Three forces act on a ring: 30 N right, 10 N left, and 5 N left. What is the net force?
Answer and explanation
15 N
Net force = 30 − 10 − 5 = 15 N to the right.
Taught alongside
- balanced forces
- unbalanced forces
- model
- evidence
- system boundary
- assumption
- interaction
- force diagram
- receiver
- normal force