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Force

ICSE Grade 10 Physics - Chapter 1

馃摎 Smart Summary

1. Introduction to Force

Force: A push or pull that changes or tends to change the state of rest or uniform motion of a body. SI unit: Newton (N).

Types of Force: Contact forces (friction, tension, normal force) and non-contact forces (gravitational, magnetic, electrostatic).

Effects of Force: Can change the speed, direction, shape, or state of rest of a body.

Balanced Forces: Forces that cancel each other out, resulting in no change in motion.

Unbalanced Forces: Forces that do not cancel out, resulting in acceleration.

2. Moment of Force (Torque)

Moment of Force: The turning effect of a force about a pivot point. Also called torque.

Formula: Moment = Force 脳 Perpendicular Distance from pivot. Unit: Newton-meter (N路m).

Clockwise and Anticlockwise Moments: Moments causing rotation in different directions.

Principle of Moments: For a body in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments about any point.

Applications: Seesaws, door handles, spanners, and other rotating systems.

3. Centre of Gravity

Centre of Gravity: The point at which the entire weight of a body appears to act.

Stability: A body is stable when its centre of gravity is low and base is wide.

Types of Equilibrium: Stable (returns to original position), unstable (moves away), and neutral (remains in new position).

Factors Affecting Stability: Position of centre of gravity and area of base of support.

4. Uniform Circular Motion

Uniform Circular Motion: Motion in a circular path at constant speed but changing velocity due to continuously changing direction.

Centripetal Force: The force directed towards the centre that keeps an object moving in a circular path.

Formula: F = mv虏/r, where m = mass, v = velocity, r = radius.

Examples: Motion of satellites, turning of vehicles, motion of electrons around nucleus.

馃搻 Formulas

Force (F) = mass (m) 脳 acceleration (a)

Newton's Second Law of Motion

Moment of Force = Force 脳 Perpendicular Distance

Calculates the turning effect of a force

Centripetal Force (F) = mv虏/r

Force required for circular motion

馃幆 Test Your Knowledge

Multiple Choice Questions

1. The SI unit of force is:

2. The moment of a force depends on:

3. A spanner with a longer handle is preferred because it:

4. The centre of gravity of a uniform rod lies at:

5. A body is in equilibrium when:

6. The force that keeps a satellite in orbit around the Earth is:

7. When a body moves in a circular path with uniform speed, its:

8. A half-metre rod is pivoted at the centre. A weight of 20 gf is suspended at 6 cm from the pivot. What weight should be suspended at 10 cm on the other side to balance it?

9. Assertion (A): A couple produces only rotational motion. Reason (R): A couple consists of two equal and opposite parallel forces.

10. The SI unit of moment of force is:

Practice Numericals

Practice Problem 1: A force of 60 N acts at the end of a spanner 30 cm long. Calculate the moment of force produced (in N路m).

Practice Problem 2: Two children of weights 40 kgf and 60 kgf are sitting on a seesaw at distances of 2 m and x m respectively from the fulcrum. If the seesaw is balanced, find x (in meters).

Practice Problem 3: A stone of mass 0.5 kg is tied to a string and whirled in a horizontal circle of radius 1 m with a speed of 4 m/s. Calculate the centripetal force (in N).

Practice Problem 4: A uniform metre scale is pivoted at its 40 cm mark. A weight of 50 gf is hung at the 10 cm mark. At what mark should a 30 gf weight be hung to balance the scale? Give answer in cm.

Practice Problem 5: A body of mass 2 kg is moving in a circular path of radius 0.5 m. If the centripetal force acting on it is 100 N, find its speed (in m/s).