Edexcel IAL Mathematics M2.4 collisions
Practise M2 collisions by combining momentum, impulse, restitution, kinetic energy loss and wall rebounds in one- or two-particle models.
- Syllabus
- First assessment 2019
- Course
- Mathematics YMA01
- Level
- A2
Practise M2 collisions by combining momentum, impulse, restitution, kinetic energy loss and wall rebounds in one- or two-particle models.
Particle P has mass 4 m and particle Q has mass 2 m.
The particles are moving in opposite directions along the same straight line on a smooth horizontal surface.
Particle P collides directly with particle Q.
Immediately before the collision, the speed of P is 2 u and the speed of Q is 3 u.
Immediately after the collision, the speed of P is x and the speed of Q is y.
The direction of motion of each particle is reversed as a result of the collision.
The total kinetic energy of P and Q after the collision is half of the total kinetic energy of P and Q before the collision.
Show that y=38u
The coefficient of restitution between P and Q is e.

Official answer figure

Official answer figure
Equation for CLM
M1
8mu-6mu=2my-4mx
A1
Equation for kinetic energy
M1
2mx2+my2=21(2m⋅4u2+m⋅9u2)
A1
17u2=2y2+(y−u)2⇒3y2−2uy−16u2=0
DM1
y=38u
A1*
Find the value of e.
After the collision, Q hits a smooth fixed vertical wall that is perpendicular to the direction of motion of Q.
Particle Q rebounds.
The coefficient of restitution between Q and the wall is f.
Given that there is no second collision between P and Q,
Use of impact law:
x+y=5eu
M1
e=5u21(38u−u)+38u
A1
e=107
A1
find the range of possible values of f.
Given that f=41
Velocity of Q after impact with the wall:
f⋅38u
B1
No second collision if
f⋅38u≤65u
M1
0<f≤165
A1
find, in terms of m and u, the magnitude of the impulse received by Q as a result of its impact with the wall.
Use
I=±2m(y−(−41y))
M1
∣I∣=320mu
A1