Quiz: Net Force Calculator
Practise adding forces and applying Newton's second law with random problems, instant feedback and a worked solution for every question.
🏋️ What is the Net Force Quiz?
The Net Force Quiz is a practice tool that generates random force problems, checks your answer instantly and shows a complete worked solution. Net force is the vector sum of every force acting on an object. It is the number that decides whether the object speeds up, slows down, turns or stays at rest, and it is the starting point of almost every mechanics problem in a first physics course.
The quiz has three levels. Easy gives two forces along one line and asks for the net force, which builds the habit of assigning signs. Medium gives three or four forces plus a mass and asks for the acceleration, so you add the forces and then apply Newton's second law. Hard uses either two forces at angles, where you resolve components and then find the magnitude or the direction of the net force, or a crate sliding against kinetic friction on a horizontal floor.
Students use a quiz like this to prepare for physics exams, to check homework strategy, and to rehearse the sign conventions that cause most lost marks. Teachers can hand out a level and a seed so that a whole class works on the same problem, while tutors can reuse a seed to revisit a question a student missed. Engineers and hobbyists meet the same ideas when they add loads on a beam, thrust and drag on a vehicle, or tension in cables.
A common misconception is that the biggest force always wins. What matters is the vector sum: a large force can be cancelled by two smaller ones pulling the other way. Another is that a moving object needs a net force to keep moving. It does not. Constant velocity means zero net force, and only a change in velocity needs a net force. The quiz is built to make these points concrete, because every answer comes with the arithmetic laid out step by step.
To compute a net force directly for your own numbers, use the Force Calculator or the Acceleration Calculator. This page is for practising the skill yourself, with a score and streak to track progress during a session.
📐 Formulas Used
📖 How to Use This Quiz
Steps to practise net force problems
💡 Example Problems
Each example opens the quiz on a specific level and seed with the correct answer filled in, so you see the full worked solution.
Example 1 — Two opposing forces (Easy, seed 3)
A 7 N force acts to the right and a 30 N force acts to the left. Find the net force (right positive).
Example 2 — Three forces and a mass (Medium, seed 1)
Forces of 28 N left, 49 N right and 32 N left act on a 10 kg object. Find its acceleration (right positive).
Example 3 — Direction of two angled forces (Hard, seed 1)
A 24 N force at 240° and a 41 N force at 135° act on an object. Find the direction of the net force.
Example 4 — Crate against friction (Hard, seed 3)
A 2 kg crate is pushed right with 10 N on a floor with μk = 0.2. Find the net horizontal force (g = 9.8 m/s²).
❓ Frequently Asked Questions
🔗 Related Calculators
What is net force in physics?
Net force is the vector sum of all the forces acting on an object. It is the single force that would have the same effect on the object's motion as all the real forces together. If the net force is zero the object does not accelerate. Otherwise it accelerates in the direction of the net force according to F = m a.
How do you find the net force when forces act in opposite directions?
Pick one direction as positive, give every force a sign, and add. For example, with right positive, 7 N right and 30 N left gives 7 + (-30) = -23 N, so the net force is 23 N to the left. Subtracting the smaller magnitude from the larger gives the same size, and the larger force sets the direction.
How do you find the net force from angled forces?
Resolve each force into x and y components using F cos θ and F sin θ, add all the x components and all the y components, then find the magnitude with the Pythagorean theorem, sqrt(Fx squared plus Fy squared). The direction is the angle atan2(Fy, Fx) measured from the positive x axis.
How do I get acceleration from the net force?
Use Newton's second law, a = F_net / m. With a net force of -11 N on a 10 kg object, the acceleration is -1.1 m/s squared, meaning 1.1 m/s squared in the negative direction. The acceleration always points the same way as the net force.
How is friction included in a net force problem?
Kinetic friction is f = μk N, where N is the normal force. On a flat floor with no vertical forces other than weight, N = m g, so f = μk m g. Friction points opposite to the direction of sliding, so with the motion to the right it is a negative term in the sum.
What tolerance does the quiz accept?
An answer is marked correct if it is within 1 percent of the exact answer or within 0.01, whichever is larger. This lets you round to two decimals without penalty. Direction questions accept an angle within 0.1 degrees, and equivalent angles such as 350 and -10 degrees are treated as the same.
What does the seed do?
The seed is a whole number fed to a pseudo-random generator. The same level and seed always create the identical question, so you can repeat a problem, share it with a classmate, or reopen it later. New question picks a fresh random seed and shows it in the seed box.
Does revealing the solution count against my score?
Pressing Show solution marks that question as already revealed, so it is not added to your score. Each question is scored only once, on the first time you check an answer, so rechecking the same problem does not inflate your streak.
Is my score saved?
No. The score and streak are kept only in memory for the current page visit. Reloading the page resets them to zero, and nothing is stored in your browser or sent anywhere.
Which value of g does the quiz use?
Friction problems use g = 9.8 m/s squared, and the value is printed in the question. If your course uses 9.81 or 10 the answers will differ slightly, so use 9.8 here to match the checker.
What is the difference between net force and the forces in a free body diagram?
A free body diagram shows every individual force on the object. The net force is what you get after adding them all as vectors. Balanced forces, such as weight and the normal force, appear in the diagram but contribute nothing to the net force.