1P May 2013 Flashcards
A power of 1 watt is the same as…
… 1 joule per second.
Uses of ultraviolet?
In water purification, tanning machines.
Why must the speed be kept low to avoid a crash?
Low speed reduces stopping distance, low momentum reduces damage if in collision, time delay increases reaction time.
If something is travelling at a constant velocity, why must the forces be balanced?
Acceleration needs an unbalanced force, constant velocity means the aeroplane isn’t accelerating.
When flying how does a paper aeroplane lose GPE?
Lost as heat.
Why would a faster / heavier plane need a longer runway to land?
Stopping distance is affected by speed and mass. For faster planes, stopping distance is greater. For heavier plane stopping distance is greater.
Explain why the ray of light is refracted towards the normal?
Change of speed and glass is denser than air.
What are the products of the fission of uranium nucleus.
Neutrons, daughter nuclei, thermal energy.
What happens in a reactor when a control rod is removed?
Rate of reaction increases, fewer neutrons absorbed by control rods, temperature increases.
Why is it difficult to make the surrounding area safe again after a serious nuclear accident?
High activity levels of radioactivity, long half-lives. Special handling equipment needed to remove sources, radioactive material mixes with the local environment.
Why does water flow and stop from one container to another when one is empty and the other is full?
Pressure difference, stops when the level is equal the pressure equality stops the flow. Pressure causes force on water.
