Explanation

He is good at mathematics.

وہ ریاضی میں اچھا ہے۔

The adjective “good” commonly takes the preposition “at.”

Good at is used to show skill or ability in a subject or activity.

Explanation

Force is defined by Newton’s Second Law:

***

1. Length – [L]  

2. Mass – [M]  

3. Time – [T]  

4. Speed/Velocity – [LT⁻¹]  

5. Acceleration – [LT⁻²]  

6. Force – [MLT⁻²]  

7. Work/Energy – [ML²T⁻²]  

8. Power – [ML²T⁻³]  

9. Pressure – [ML⁻¹T⁻²]  

10. Density – [ML⁻³]  

11. Momentum – [MLT⁻¹]  

12. Impulse – [MLT⁻¹]  

13. Gravitational constant (G) – [M⁻¹L³T⁻²]  

14. Planck’s constant (h) – [ML²T⁻¹]  

15. Charge – [TI] (T = time, I = current)  

16. Potential difference (Voltage) – [ML²T⁻³A⁻¹]  

17. Electric current – [I]  

18. Electric resistance – [ML²T⁻³A⁻²]  

19. Capacitance – [M⁻¹L⁻²T⁴A²]  

20. Magnetic field (B) – [MT⁻²A⁻¹]

Explanation

90 percent *90

= (90/100)*90

= (90*90)/100

= 8100/100

= 81

Question updated 03-March-2026

Explanation

• A wave transmits energy from one place to another
• Waves are disturbances that propagate through a medium.
• Particles of the medium oscillate around equilibrium but do not travel with the wave.
• The motion of particles transfers energy, not matter.
• Energy is carried in the form of kinetic and potential energy of oscillating particles.

Last updated question 25 feb 2026

Explanation

• A knife is a tool used to cut, similarly a pen is a tool used to write.
• This is an example of a tool-to-function analogy.

Last verified on 15-02-2026

Explanation

The RMS (Root Mean Square) value of an AC waveform is the effective or equivalent DC value that produces the same heating effect (power dissipation) in a resistor as the AC signal

 It is calculated as the square root of the mean of the squares of instantaneous values over one cycle.

For a sinusoidal AC wave:

• At 0°, the instantaneous value is zero (minimum).

• At 90°, the instantaneous value reaches its maximum.

Therefore, the RMS-related peak behavior corresponds to maximum at 90° and minimum at 0°.

Last updated 14-feb-2026

Explanation

70 × 70 = 4900, and 4900 ÷ 100 = 49.

Last updated 14-feb-2026

Explanation

Silicon is widely used in semiconductors because:

• It is abundant in nature.
• It has suitable electrical properties.
• It has excellent thermal stability.
• It forms a stable oxide layer (SiO₂) useful in device fabrication.

Note: Germanium was used earlier, and gallium nitride is used for high-power or high-frequency devices, but silicon remains the standard.

Last updated 14-feb-2026

Explanation

The total percentage of silicon in the Earth's crust is approximately 27.7% by weight.

Additional information

Abundance: Second most abundant by weight (~ 28%) and volume (0.9%).

Occurrence: It does not exist in pure form in nature, but rather as oxides (e.g., sand, quartz) and silicates (e.g., feldspar, mica, clay).

Last updated 14-feb-2026

Explanation

• Pressure is a fundamental physical quantity that is defined as the force exerted per unit area.
• It is a measure of the strength of a force acting on a surface.
• It is typically measured in units such as Pascals (Pa) or pounds per square inch (PSI).

Last verified on 10-02-2026