Explanation

Efficiency is the ratio of output to input, often expressed as a percentage.

It represents how much of the input energy is actually converted into useful output energy, with the rest being lost as waste or heat.

Key Points:

• Energy is the ability to do work.
• Work is the transfer of energy through a force applied over a distance.
• Power is the rate at which work is done or energy is transferred.

Explanation

When a gas is heated in a container of fixed volume, the molecules of the gas:

• Move faster (their kinetic energy increases, causing them to move more rapidly)
• Collide more frequently with the container walls (resulting in increased pressure)
• Do not expand (the container volume is fixed)
• Do not move further apart (the density of the gas remains the same, as the volume

Explanation

Neutral equilibrium is a state where the body is balanced, but the slightest disturbance will not cause it to return to its original position or topple over.

In this state, the center of gravity (CG) remains at the same height, regardless of the slight tilt or displacement.

Key Points: 

• A body is in unstable equilibrium after slight tilt if its center of gravity remains above the point of contact.
  
• A body is in stable equilibrium after slight tilt if its center of gravity remains above the point of contact.
  

Explanation

To find the density of the steel balls, we need to use the formula for density:

Density = Mass/Volume

1. Calculate the total mass of the steel balls:

Each ball has a mass of 27 g, and there are 10 balls.

Total mass = 10 x 27 = 270 g

2. Calculate the volume displaced by the steel balls:

The initial volume of water is 20 cm^3

The final volume of water is 50 cm^3

The volume displaced by the steel balls is:

Volume displaced = 50 cm^3 - 20 cm^3 = 30 cm^3

3. Calculate the density of the steel:

Using the total mass and the volume displaced:

Density = 270 g / 30cm,^3 = 9.0 g/cm^3

Therefore, the density of the steel is 9.0 g/cm^3.

Explanation

Heat conduction is a process in which heat is transferred from the hotter part to the colder part in a body without involving any actual movement of the molecules of the body.

AGM 25-12-2022

Explanation

If A · B = 0, it means the vectors A and B are perpendicular.

The magnitude of the cross product is:

|A × B| = |A||B|sinθ

For perpendicular vectors, θ = 90°, so sin(90°) = 1

⇒ |A × B| = AB × 1 = AB

Explanation

The main source of energy in stars is nuclear fusion.

It is the process of combining atomic nuclei (usually hydrogen nuclei) to form a heavier nucleus, releasing vast amounts of energy in the process.

This energy is what makes stars shine.

Explanation

Ultrasound has several medical applications, including:

• Pre-natal scanning
• Diagnostic imaging
• Cancer treatment

In industry, ultrasound is used for:

• Cleaning and deburring
• Welding and bonding
• Non-destructive testing

Explanation

The rate of evaporation can be increased by:

• Decreasing atmospheric pressure
• Increasing temperature
• Decreasing humidity
• Increasing the surface area of the liquid

Explanation

The boiling point is the temperature at which a pure liquid changes state from liquid to gas at standard atmospheric pressure.

Key Points:

• The melting point is the temperature at which a solid changes state to a liquid.
• The freezing point is the temperature at which a liquid changes state to a solid.