Explanation

A rocket expels gases backward, and by Newton’s 3rd law, it gains forward thrust.

This works on the principle of conservation of momentum.

Explanation

Radiation transfers energy without any medium, unlike conduction or convection.

Sun’s energy reaches satellites in space through electromagnetic waves (radiation).

Explanation

Step 1: Interpret the problem
The car moves in 3 phases:

1. Average speed = $20\text{ m/s}$ for $2.0\text{ s}$

2. Average speed = $40\text{ m/s}$ for $2.0\text{ s}$

3. Average speed = $60\text{ m/s}$ for $6.0\text{ s}$

We want the overall average speed = total distance / total time.

Step 2: Calculate distances in each phase
Using $\text{distance}=\text{average speed}\times \text{time}$:

• Phase 1: $20\times 2.0=40\text{ m}$

• Phase 2: $40\times 2.0=80\text{ m}$

• Phase 3: $60\times 6.0=360\text{ m}$

Total distance $=40+80+360=480\text{ m}$

Step 3: Total time
$2.0+2.0+6.0=10.0\text{ s}$

Step 4: Overall average speed

$${\mathrm{<b><font\; color="\#0000ff">v</font></b>}}_{\text{<b><font color="\#0000ff">avg</font></b>}}<b><font\; color="\#0000ff">=</font></b>\frac{\mathrm{<b><font\; color="\#0000ff">480</font></b>}}{\mathrm{<b><font\; color="\#0000ff">10</font></b>}}<b><font\; color="\#0000ff">=</font></b>\mathrm{<b><font\; color="\#0000ff">48</font></b>}\text{<b><font color="\#0000ff"> m/s</font></b>}$$

Explanation

Each slit diffracts the light, and these diffracted waves interfere with each other.

Thus, the observed fringe pattern is due to interference + diffraction together.

Explanation

At constant volume, no work is done, so heat supplied increases the internal energy.

This rise in internal energy appears as an increase in temperature.

Explanation

The student’s values (1.65, 1.72, 1.89) are close to each other → shows precision.

But they differ from the true value (2.35) → means not accurate.

Explanation

We apply Boyle’s Law:

P1​V1​ = P2​V2​
760×500 = P2​×300
P2 ​= 500×760 = 300​ = 1266.67torr

Explanation

Amplitude ↑: More air energy → greater displacement of molecules.

Intensity ↑: Higher amplitude → louder sound (more energy).

Explanation

0°C → 4°C: Volume decreases as ice-like structure breaks, molecules pack closely → maximum density at 4°C.

4°C → 10°C: Volume increases as molecules move apart due to higher kinetic energy.

Explanation

In constructive interference, waves superpose in phase, so amplitudes add up.

As intensity ∝ (amplitude)², the resultant intensity becomes greater than the individual intensities.