6p1 Further Mechanics Flashcards
(12 cards)
What are the letters and units in the equation
Ft = p
F - force (N)
t - impact time (s)
p - momentum (kgm/s)
What is impulse
change of momentum and the equation is I = F x t
What is the approach to solve problems of conserving momentum in two dimensions
resolve motion into components along perpendicular axes - solve resultant pair of problems in one dimension
whats the difference between elastic and inelastic collisions
elastic is where both momentum and kinetic energy are conserved whereas inelastic is when only momentum is conserved as kinetic energy is converted into other forms
which collision is it if objects stick together afterwards
inelastic collision
how to derive the equation for non-relativistic particles kinetic energy
Ek = 1/2mv^2 with p = mv
sub v = p/m into the Ek equation
to get Ek = 1/2m(p^2/m^2)
and simplify for Ek = p^2/2m
what do we know about an object moving in a circular path with a constant speed
constantly changing velocity as its constantly changing direction therefore the object is accelerating which is known as centripetal acceleration - we know from newtons first law that acceleration required a resultant force so an object moving in a circular path must experience a force which we call the centripetal force that acts towards the centre of the circle
How to investigate the relationship between force exerted on an object and its change in momentum
1) set up apparatus with a slightly tilted ramp and a pulley attached to the lower end of the ramp, attach a string with a hanging mass to the trolley and pass the string over the pulley, set up two sets of light gates on either side of the ramp parallel to each other
2) place masses and card inside the trolley and then measure the mass of the system with the string and then the mass of just the trolley
3) measure length of the card
4) release trolley from top of ramp such that hanging mass will fall vertically
5) light gates time at that light gate and velocity = L/t where t is initial velocity at first light gate and final velocity and second light gate
6) p = Mv to find change of momentum so force = p/t where p is momentum
7) repeat 3 times and calculate mean force, repeat procedure moving masses from trolley to hanger
8) plot F against p/t to give a straight line supporting Ft = P
why should the runway be tilted in the momentum experiment
to compensate for the friction that will act on the trolley
How will friction affect results in momentum experiment
friction reduces resulting force acting on trolley causing decreased velocity and shallower gradient of graph
how to use ICT to analyse collisions between small spheres
1) measure masses of two spheres using a mass balance
2) position two metre rulers perpendicular to each other using a set square
3) position a video camera above the table top (bird’s eye view) and start recording
4) roll one sphere towards the stationary sphere, allow them to collide and roll and wait for them to come to rest
5) import video to tracking software and calibrate distance using metre rules
6) go through each frame and calculate distance travelled and calculate time between each frame so use V = sqrt(Vx^2 + Vy^2) where Vx is horizontal components and Vy is vertical
7) angle of travel can also be calculated with trig
8) use velocities to show initial and final momentum is conserved in both horizontal and vertical plane
why would a car slide off a circular track
the frictional force is not large enough
