1. What is the difference between speed and velocity?
In everyday language, speed and velocity are used interchangeably. In physics, the distinction is critical: speed is a scalar, and velocity is a vector.
Speed simply tells you how fast an object is moving (e.g., 60 mph). It is calculated as distance traveled divided by time. Velocity tells you how fast an object is moving and in what direction (e.g., 60 mph North). It is calculated as displacement divided by time.
If you drive in a circle and end up exactly where you started, your average speed might be 60 mph, but your average velocity is exactly zero because your net displacement is zero!
2. How does a transformer work?
Transformers are devices that step up or step down voltage in AC (alternating current) circuits. They operate entirely on the principle of electromagnetic induction discovered by Michael Faraday.
A transformer consists of two coils of wire (primary and secondary) wrapped around a common iron core. When AC flows through the primary coil, it creates a constantly changing magnetic field in the core. This changing magnetic field passes through the secondary coil, inducing an alternating voltage in it.
The ratio of the voltages is equal to the ratio of the number of turns in the coils. If the secondary coil has twice as many turns as the primary, the voltage is doubled (step-up transformer).
3. What is the law of conservation of momentum?
The law states that in a closed system (one with no external forces acting on it), the total momentum before an event is exactly equal to the total momentum after the event. Momentum is defined as mass times velocity (p = mv).
This is why when a stationary astronaut throws a wrench in space, the astronaut is pushed backward. The initial momentum was zero. To keep the total momentum at zero, the forward momentum of the wrench must be perfectly canceled out by the backward momentum of the astronaut.