Physics Chapter on Work, Energy, Power, and Gravitation

Study Notes

Work

Work is performed when a force moves an object through a distance in the same direction as the force.
SI unit of work is joule.

Energy

Energy is a scalar quantity, with its unit also being joule.
Total energy in an isolated system is conserved, referred to as the law of conservation of energy.

Power

Power is measured in watts.
1 watt hour equals 3600 joules.
1 kilowatt hour equals 3.6 × 10⁶ joules.
1 horsepower (HP) is equivalent to 746 watts.

Gravitation

Every object in the universe attracts others through a gravitational force.
The gravitational force exerted by the Earth is termed gravity.
Acceleration due to gravity (g) is approximately 9.8 m/s² and is constant for objects regardless of shape or mass.
Escape velocity is the speed needed to overcome Earth's gravitational pull; it is 11.2 km/s on Earth and 2.4 km/s on the Moon, which lacks an atmosphere due to the low escape velocity.
Value of g decreases with height or depth from the Earth's surface, maximizes at the poles, and minimizes at the equator.
g reduces if Earth's angular speed increases and increases if angular speed decreases.
On the Moon, g is one-sixth that of Earth, making a person's weight there also one-sixth of what it is on Earth.

Satellite

Satellites are objects (natural or artificial) orbiting planets due to gravitational attraction.
The Moon is a natural satellite; INSAT-B is an artificial satellite.
A satellite near Earth's surface orbits every 1 hour and 24 minutes.
Geo-stationary satellites orbit at around 36,000 km and complete a rotation every 24 hours.
Earth rotates from West to East, causing celestial bodies to appear to move from East to West.
Geosynchronous satellites maintain an orbital period matching Earth’s rotation.
A special category, geostationary satellites, orbits directly above the equator in a circular path.
Geo-stationary satellites are used for broadcasting, weather forecasting, and predicting natural disasters.
Polar satellites orbit at approximately 800 km with a period of 84 minutes.

Cathode Rays

Discovered by Sir William Crookes, cathode rays travel in straight lines.
They cause fluorescence and can penetrate thin metal foils.
Cathode rays are deflected by electric and magnetic fields.
Their velocity ranges from 1/30th to 1/10th the speed of light.

Description

This quiz covers key concepts related to work, energy, power, and gravitation. It explores definitions, units of measurement, and the fundamental principles governing these topics in physics. Test your understanding and application of these essential principles.