3 - momentum and collisions

Question 1

momentum

Answer 1

mass * velocity
in kgms^-1

Question 2

impulse

Answer 2

Force*time = change in momentum
I = Ft = mv- mu
measured in Ns

Question 3

contact and impulse

Answer 3

at the time of contact for which the collision force acts the same for both balls - impulse is the same but in opposite directions
(total I = 0)

Question 4

conservation of linear momentum

Answer 4

total momentum before collisions = total momentum after

Question 5

combining masses

Answer 5

when objects move of together or coalesce they combine into one object (masses add)

Question 6

modelling collisions assumptions

Answer 6

• spheres are smooth
• impulse acts along the line of centres
• non of the spheres are spinning

Question 7

perfectly elastic collision

Answer 7

no KE is lost from the system
total KE will remain the same

Question 8

perfectly in elastic collision

Answer 8

spheres coalesce
momentum is conserved
maximum KE is lost

Question 9

neither elastic or in elastic

Answer 9

momentum is conserved and some KE is lost but they don’t coalesce

Question 10

coefficient of restitution

Answer 10

speed of separation/ speed of approach = e
v2 - v1/ u1 - u2 = e
0<= e<= 1
depends of the material properties of the object

Question 11

if e = 1

Answer 11

there is no loss of KE
perfectly elastic collision

Question 12

if e = 0

Answer 12

maximum loss of KE
inelastic collision

Question 13

for collisions between moving and fixed objects

Answer 13

-v1/ u1 = e
v = -eu