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What is momentum, and how is it conserved in collisions?
Momentum is the product of mass and velocity (p = mv), measured in kg⋅m/s. In any collision, the total momentum before equals the total momentum after, as long as no external forces act on the system. Step-by-Step Solution: Calculate momentum using p = mv (mass × velocity) For collisions: p₁(before) + p₂(before) = p₁(after) + p₂(after) In elastic collisions, both momentum AND kinetic energy are conserved In inelastic collisions, only momentum is conserved (energy is lost as heat/sound) Verify your answer: Total momentum before = Total momentum after Key Mistake to Avoid: Students often forget that momentum has direction (it's a vector), so signs (+ and -) are crucial when solving collision problems. Required for: Combined Science and Physics Quick Tip: Always draw a before/after diagram for collision questions, marking directions with arrows and clearly showing + and - velocities.
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Explain the purpose of each wire (live, neutral, earth) in a UK three-pin plug.
Each wire in a UK three-pin plug serves a specific safety and functional purpose - Live (brown) carries the current in, Neutral (blue) completes the circuit, and Earth (green/yellow) provides emergency protection. Step-by-Step Solution: Live wire (brown) - Carries 230V alternating current from the mains supply to th
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Explain reflection and refraction of light waves using ray diagrams.
Reflection and refraction are behaviors of light waves where light either bounces off surfaces (reflection) or changes direction when passing through different mediums (refraction). Step-by-Step Solution: Reflection: Draw incident ray, normal line (90° to surface), and reflected ray. Angle of incidence (i) = angle o
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Explain why a charged comb can attract small, neutral pieces of paper.
A charged comb attracts neutral paper through electrostatic induction, where the charge on the comb causes temporary charge separation in the paper. Step-by-Step Solution: When the negatively charged comb approaches, it repels electrons in the paper This creates a temporary positive charge on the near side of the p
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Calculate the current flowing through a 10-ohm resistor connected to a 20-volt power supply using Ohm's Law.
The current flowing through the 10Ω resistor is 2 amperes (A). Step-by-Step Solution: Recall Ohm's Law: V = IR (where V=voltage, I=current, R=resistance) Rearrange formula to find current: I = V/R Insert values: I = 20V ÷ 10Ω Calculate: I = 2A Verify units match: volts/ohms = amperes ✓ Key Mistake to Avoid: Don
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