Explore how forces combine when objects are pushed or pulled!
📚 Learning Index
1. What is Force?
A force is a push or a pull acting on an object. Force can change the speed, direction or shape of an object.
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Push
A person pushes a box away.
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Pull
A person pulls an object towards them.
Unit of force: Newton (N)
When several forces act on an object, their combined effect is called the net force or resultant force.
2. Forces Acting in the Same Direction
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When two or more forces act in the same direction, their magnitudes are added.
Example:
Person A pushes with 10 N.
Person B pushes with 15 N.
Net force = 10 + 15 = 25 N →
3. Forces Acting in Opposite Directions
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When forces act in opposite directions, subtract the smaller force from the larger force.
Example:
Rightward force = 30 N
Leftward force = 20 N
Net force = 30 − 20 = 10 N →
If both forces are equal, the net force is zero. The forces are balanced.
4. Force Applied by One Person
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One person applies a force of 20 N towards the right.
Net force = 20 N towards the right.
5. Force Applied by Two Persons
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Two people push in the same direction. Their forces add together.
15 N + 20 N = 35 N towards the right.
6. Force Applied by Three Persons
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Three people push a box in the same direction.
10 N + 15 N + 20 N = 45 N towards the right.
7. Interactive Net Force Experiment Lab
Choose an object, number of persons, force magnitude and direction. Watch the object move according to the resultant force.
FORCE IN ACTION
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←→
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LEFT SIDE ← RIGHT SIDE →
For this experiment, the action direction is the direction in which the force acts on the object. The people are illustrated symbolically on opposite sides.
📊 Force Measurement
Apply forces to see the results here.
8. Student Assessment
Calculate the net force and choose the correct answer.
Your score will appear here.
⭐ Remember
Force is a push or a pull.
Same direction forces are added.
Opposite direction forces are subtracted.
Equal and opposite forces produce zero net force.
Net force is measured in Newtons (N).
A non-zero net force changes the motion of an object.
🎙️ Audio Narration
Welcome to the Net Force Simulator. Select an activity and press the buttons to listen to the explanation.
For audio, allow sound in your browser and enable the device media volume. Use the Listen buttons to start narration.
Identify centre, radius, diameter and circumference.
Understand how to draw a circle.
Derive the formulas for circumference and area.
Calculate perimeter and area using radius.
Solve numerical problems independently.
Explore the Topics
1. What is a Circle?
A circle is a closed plane figure consisting of all points in a plane that are at the same fixed distance from a fixed point.
Definition: The fixed point is called the centre, and the fixed distance is called the radius.
Examples in daily life
Clock face, bicycle wheel, coins, circular plates, bangles and roundabouts.
2. Important Parts of a Circle
Centre: The fixed point inside a circle.
Radius: Distance from centre to any point on the circle.
Diameter: A straight line passing through the centre and joining two points on the circle.
Circumference: The total boundary length of the circle.
Chord: A line segment joining two points on the circle.
Diameter = 2 × Radius
Radius = Diameter ÷ 2
3. How to Draw a Circle
Required materials: Compass, pencil, ruler and paper.
Mark a point on the paper. Name it O.
Measure the required radius using a ruler.
Open the compass to the measured distance.
Place the compass needle at O.
Rotate the pencil arm completely around O.
A circle is formed.
Remember: Keep the compass opening unchanged while drawing the circle.
4. Derivation of Formulas
A. Perimeter or Circumference
The perimeter of a circle is called its circumference. It is the total length around the circular boundary.
For every circle, the ratio of circumference to diameter is a constant called pi.
π = Circumference ÷ Diameter
Therefore,
Circumference = π × Diameter
We know that diameter = 2 × radius.
C = 2 × π × r
B. Area of a Circle
Area is the amount of surface enclosed within the circular boundary.
Imagine cutting a circle into many small sectors and arranging them alternately to form an approximate rectangle.
The approximate rectangle has:
Length = Half the circumference = πr
Breadth = Radius = r
Area of rectangle = Length × Breadth
Area = πr × r
A = πr²
Important: Use π = 22/7 or 3.14 as specified in the question. The sector rearrangement gives an exact limiting derivation as the number of sectors increases.
Units
Circumference is measured in centimetres (cm).
Area is measured in square centimetres (cm²).
5. Interactive Circle Simulator
Select a radius and observe how the circle changes.
Circle with radius 3 cm
Selected radius = 3 cm
Perimeter / Circumference
Formula: C = 2 × π × r
Area of Circle
Formula: A = π × r × r
This simulator uses π = 3.14 and displays answers to two decimal places.
6. Student Assessment
Enter the correct perimeter and area for each given radius.
