Review of Physics Concepts

Flashcards based on lecture notes about physics concepts including forces, motion, energy, and waves.

What factors affect the drag force on a high-speed train?

The factors are the speed of the train, the shape of the train, the direction of any wind, and the viscosity of the air.

Describe how the forces acting on a parachutist change during different stages of a jump (A, B, C, D, F, G, as described in the lecture notes).

At A: velocity is zero, air resistance is zero, unbalanced force is downwards due to gravity. At B: air resistance increases with velocity, so the unbalanced force is smaller. At C: velocity reaches terminal velocity, upward air resistance equals downward gravity, unbalanced force is zero. At D: parachute opens, air resistance greatly increases, unbalanced force is upwards, velocity decreases. At F: parachutist slows, upward air resistance decreases, unbalanced upward force is smaller. At G: parachutist slows to a new, lower terminal velocity where upward air resistance equals downward gravity again; unbalanced force is zero once more.

What is the formula for momentum?

Momentum = mass × velocity

What is an unbalanced force?

A force that is not balanced by a force in the opposite direction

What is the equation relating force, mass, and acceleration?

Force = mass × acceleration (F = ma)

What is thinking distance?

The distance a car travels after the driver has seen a hazard but before the driver applies the brakes.

What is braking distance?

The distance travelled by the car after the driver has started braking and the car is decelerating to rest.

What is overall stopping distance?

The sum of the thinking distance and the braking distance.

On what does the braking distance of a car depend?

The speed that the car is travelling and the braking force that can be applied without the car skidding.

List the waves in the electromagnetic spectrum.

Radio waves, microwaves, infra-red waves, visible spectrum, ultraviolet waves, X-rays, gamma rays.

What characteristics do all electromagnetic waves share?

Transfer energy, are transverse waves, travel at the speed of light in a vacuum, can be reflected, refracted and diffracted.

How does the amplitude of a sound wave affect the loudness of the sound?

When the source is vibrating with a small amplitude, the disturbance of each air particle as the wave passes is fairly small and the sound is quiet. If the source is vibrating with a large amplitude, the particles are displaced further from their rest position as each wave passes, and we hear a louder sound.

Describe the energy transformations in a lamp powered by a battery.

Stored chemical energy in the battery → electrical energy in the circuit → heat and light in the lamp filament.

Why are kettles often made of copper with a shiny surface?

Copper conducts heat quickly, while a shiny surface reduces heat loss by thermal radiation.

What is the formula for weight?

Weight = mass × gravity

What is power and how is it calculated?

Power is the rate of doing work (or the rate of converting energy) and can be calculated using power = work done in J ÷ time taken in s. The unit of power is the watt.

What are some disadvantages of hydroelectricity?

Needs large reservoirs, which may displace people and/or wildlife. Can be built only in hilly areas with plenty of rainfall.

What are some advantages of hydroelectricity?

clean – no waste products

What is a key environmental factor about biomass energy?

The carbon dioxide it releases when it burns has only recently been taken out of the atmosphere by crops.

What are some potential disadvantages of biomass energy?

Growing biomass crops instead of food can cause higher food prices and/or food shortages.

What are some disadvantages of wind energy?

Only produce energy when it is windy. Can be used only in certain places. Can be an eyesore.

What are some disadvantages of solar energy?

Expensive in terms of amount of energy produced. Not very efficient method of converting energy into electricity.

What are some disadvantages of wave energy?

Expensive to set up. Only suitable in certain locations.