3 Physics - Motion, Matter, and Forces
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equation speed
distance ________ = speed time
what is velocity?
speed in a given direction
what does the gradient represent in a distance vs time graph?
the speed
equation acceleration
final velocity - initial velocity ______________________ = acceleration m/s^2 time
in a speed vs time graph, how do you find the distance travelled?
it is the area under the line
what is density?
the amount of matter in a given volume
equation density
mass ______ = density (g/cm^3 or g/ml^3) volume
describe and explain the 4 effects of force on objects
deformation - when a force changes shape of object acceleration - unbalanced forces can cause an object to accelerate oppose motion - friction and air resistance are examples of forces that make motion more difficult upthrust - keeps objects from sinking in water & allows planes to fly
what is newtons first law of motion?
mass resists motion an object at rest will stay at rest, unless acted upon by an unbalanced force an object at a constant velocity remains so, unless acted upon an unbalaced force
unit of force
newtons (N)
what happens if opposite forces are balanced/unbalanced?
if they are balanced it stays at constant speed if it is unbalanced it accelerates
what is resultant force?
if you have 20N acting to the right and 15N acting to the left, you have 5N of resultant force to the right
what is limit of proportionality/hooke’s law?
http://www.mindset.co.za/resources//0000022668/0000029750/0000029690/da000215__110249.jpg
equation for force?
f = mass x acceleration
what is pressure dependent on?
force and area
what is the unit of pressure?
N/m^2
what is equation for pressure?
force _____ = pressure area
why is it safer to lay down on ice than to stand on ice?
because you have the same force but when you lay down you have a greater area, which means that the force is more spread out, and there is less pressure so the ice is less likely to break
why does a knife have a sharp edge?
it makes the area to which the force is being applied smaller, increasing pressure, making it easier to cut
how does a tractor’s big tyres stop it sinking too far into soft soil?
the big area spreads out the weight, decreasing pressure