คำถามทบทวนความรู้

การแทนที่

• The gradient of a displacement-time graph is velocity. The area under a velocity-time graph gives displacement. A constant-acceleration formula is valid only when its assumption is justified.

2 m/s²

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เวลาหยุดนานขึ้น

• Impulse equals momentum change. Increasing stopping time for the same momentum change reduces average force. Identify external forces before applying momentum conservation.

6 กก.·ม./วินาที

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เพิ่มเป็นสี่เท่า

• Define the system and useful output before calculating efficiency. Doubling speed quadruples kinetic energy at constant mass. Power describes transfer per time, not total energy.

60 %

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

คานงัดตั้งฉากที่ยาวขึ้น

• For a rigid body about a fixed axis, net torque equals moment of inertia multiplied by angular acceleration. Rotational kinetic energy depends on angular speed squared. Angular momentum is conserved when net external torque is zero.

3 N m

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ในกรอบหยุดนิ่งของวัตถุ

• The Lorentz factor is 1 divided by the square root of 1 minus speed squared over light speed squared. Galilean velocity addition is an approximation for speeds much smaller than light speed.

10 μs

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

พลังงานเปลี่ยนการจัดเรียงของอนุภาค

• Temperature relates to particle motion in a model; internal energy includes kinetic and potential contributions. During a change of state, energy can change particle arrangements rather than temperature.

3000 J

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

การยกอุปกรณ์ไฟฟ้าที่เปราะบางให้สูงกว่าระดับน้ำท่วมที่คาดไว้

• Distinguish mitigation, which addresses drivers, from adaptation, which reduces harm from impacts. A policy assessment needs evidence about effectiveness, cost, equity and uncertainty; one criterion is not the entire decision.

30 %

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เคลวิน

• At fixed amount and volume, pressure is proportional to kelvin temperature. At fixed temperature and amount, pressure is inversely proportional to volume. State which quantities are fixed before choosing a relationship.

140 kPa

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

พลังงานภายในเพิ่มขึ้น

• State a sign convention before using the first law. Here change in internal energy equals heat into the system minus work done by the system. Expansion work can reduce internal energy when no heat enters.

300 J

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เชื่อมต่อขนานกับตัวต้านทาน

• Current is the same through components in series. Potential differences add around the series path. In parallel, branches share the same potential difference, while branch currents sum at a junction.

30 Ω

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ที่ภาวะสมดุล

• Velocity is greatest near equilibrium for ideal SHM, while acceleration magnitude is greatest at extreme displacement. Resonance can occur near the natural frequency under periodic driving, with amplitude limited by damping.

1.5 s

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ความถี่

• At a boundary, frequency stays fixed by the source. A change of speed changes wavelength. Refraction follows from speed differences; angles are measured from the normal.

2 m/s

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

การถอยห่างในแนวสายตา

• Compare a identified line with its laboratory rest wavelength. Use z = (observed−rest)/rest, then v approximately cz in the stated low-speed model. Do not apply this approximation without checking the regime or treating a cosmological redshift as a simple exact velocity.

0.002

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ระยะห่างระหว่างหน้าคลื่นเล็กลง

• For a source approaching a stationary observer along the line of sight, f observed = f source × v/(v−v source). Recession uses v+v source in the denominator. These are sound-wave models; light requires its appropriate relation.

637.5 Hz

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เข้าหาจุดศูนย์กลาง

• For a point mass or outside a spherical mass, field strength follows an inverse-square distance dependence. Use distance from the centre, not height above the surface alone.

2

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เปลี่ยนทิศทางในสนามเดิม

• In a uniform field between ideal parallel plates, E = V/d away from edge effects. The force is F = qE, so its direction reverses for a negative charge. Coulomb force between ideal point charges decreases with separation squared.

4000 V/m

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ทิศทางการเคลื่อนที่

• Equate magnetic force with mv²/r to obtain r = mv/(|q|B) for perpendicular motion. A stronger field makes a smaller radius at fixed momentum. Parallel entry gives zero magnetic force in this model.

0.2 m

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

การเชื่อมโยงฟลักส์ที่เปลี่ยนแปลง

• Changing field strength, coil area, orientation or relative motion can change flux linkage. Lenz law describes an induced effect opposing the change producing it, consistent with energy conservation.

5 V

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ผลต่างพลังงานลดลงที่มีค่ามากกว่า

• An emitted photon corresponds to a transition to a lower energy level. Absorption requires a compatible energy difference. Rutherford scattering supported a small dense nucleus, but that experiment alone did not establish the complete quantum model.

5 eV

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

จำนวนอิเล็กตรอนที่ปล่อยออกมาต่อหน่วยเวลา

• Use photon energy = Planck constant × frequency. Maximum kinetic energy = photon energy - work function. Increasing intensity at fixed frequency increases photon arrival rate, not individual photon energy.

2.7 eV

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ค่านับที่วัดได้ลบด้วยค่าพื้นหลังในช่วงเวลาเท่ากัน

• Subtract background counts measured over the same time interval. Distinguish irradiation from contamination. Shielding, distance and reduced exposure time can reduce risk under a school-controlled procedure.

20 ครั้ง/นาที

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

นิวตรอนที่ปล่อยออกมาเริ่มการฟิชชันเพิ่มเติม

• Separate conservation of nucleon number from conservation of total energy. Released neutrons may initiate further fissions, escape or be absorbed. A controlled reactor and an uncontrolled chain reaction have different neutron-management conditions.

3 นิวตรอน

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

ลดลงเหลือหนึ่งในสี่

• For isotropic emission without absorption, flux follows an inverse-square relationship with distance. Observed brightness alone therefore cannot establish luminosity.

2

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.

เครื่องชั่งอ่านค่า 0.20 g เมื่อว่างเปล่า

• For a product or quotient, adding fractional uncertainties is a common maximum-uncertainty approximation. For a difference, add absolute uncertainties. A nonzero intercept can reveal an offset or an incomplete model.

2.5 %

• Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.