P12 Newton’s Laws Flashcards
inertia
tendency of an object to remain in a steady state (i.e., at rest or moving in a straight line at a constant speed)
Newton Law I
velocity, speed, dirrction of an object will only change if a resultant force is acting on it
5 what can a change in velocity mean
the object:
starte to move
stops moving
speeds up
slows down
changes direction
these can ONLY happen if there is a resultant force acting on the object
Newton Law II
F = ma
inertial mass (kg)
force/acceleration
* this is also newton’s second law
Newton Law III
whenever 2 objects interact, they exert equal and opposite forces on each other
4 characteristics of force pairs
act on separate objects
are the same size
act in opposite direction along the same line
are of the same type (gravitational, electrostatic etc)
momentum (eq and units)
vector quantity
units are kg m/s
momentum = mass x velocity
p = mv
law of conservation of momentum
in a closed system, total momentum before an event = total momentum after an event
so:
m1u1 + m2u2 = m1v1 + m2v2
why is momentum conserved in explosions
total momentum before is 0
total momentum after is also 0 - different parts of the object travel in different directions so the momentum of each part will cancel out with the momentum of another part
what happens when two objects recoil off each other
they start with total momentum = 0, and move away from each other with velocities v1 and v2
so:
m1v1 + m2v2 = 0
experiment to investigate relationship between mass and acceleration
attach trolley to string with hanging mass over pulley or diagram
keep force constant
use motion sensor/light gates to measure velocities and times/acceleration
change mass measure acceleration
repeat several times and find mean
why does friction reduce acceleration
reduces resultant force
