Physics
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What is mass and what are its units?
Amount of matter and Kg
What is weight and what are it’s units?
Effect of gravitational field on mass. Newtons
What is the formula for working out weight?
W = mg (g=10 on earth)
What is the formula for density?
Density = mass divided by volume
How do work out volume?
Drop object in water and see how much level goes up by
What is friction and what does it cause?
Force that opposes movement and it causes heat and wear and tear
What is a force and what are they measure in?
Push or pull - Newtons
What is air resistance?
Friction of the air when an object moves
What is resultant force? What does it cause?
Overall force - acceleration of the object in that direction
What is no resultant force called an what happens?
Balanced - object travels at a constant speed
In Hook’s law a spring obeys F=kx What does F, k and x stand for?
F = force, k = spring constant, x = extension of the spring
How do you calculate k in Hook’s law?
Gradient of the graph
When does a spring reach its elastic limit on a graph?
No longer straight line
Why does an elephant cause less pressure on the floor than a woman in high heels?
Even though it has more weight (force) it has much less area so has less force per area (P = F/A)
Why do hot things expand?
Particles move faster and further away
What does evaporation cause cooling?
More energetic particles escape at the surface of a liquid to become a gas. Ones left behind have less energy so cooler
How can you speed up evaporation?
hotter, larger surface area, wind
How is heat transferred in solids and how does it happen?
Conduction - hotter particles vibrate more and collide with ones next to them passing on energy
How is heat transferred in liquids and gases and how does it happen?
Convection - hotter particles move faster and further apart so become less dense and rise
Which is the only way heat can transfer in a vacuum?
Radiation in the form of waves
What do like charges do?
Repel
What do opposite charges do?
Attract
How does something end up with a positive charge?
Loses electrons
How does something end up with a negative charge?
Gains electrons