Mathematics · Oct / Nov 2025 · Paper 51 · Question 2
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As printed in the paper
The question as text
2. ku u P Q 7m 3m Figure 2 Particle P of mass 7m and particle Q of mass 3m are moving in opposite directions along the same straight line on a smooth horizontal surface. The particles collide directly. Immediately before the collision, the speed of P is ku and the speed of Q is u, as shown in Figure 2. Immediately after the collision, the speed of P is w and the speed of Q is 2w. The direction of motion of Q is reversed by the collision. The impulse received by Q in the collision has magnitude 7 2 mu.
Read automatically from the paper; the printed page above is exact.
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2(a)[3]
ku
u
P
Q
3m
7m
either
w
2w
or
w
2w
Use of I
=
mv mu
−
for Q
7
(
)
(
)
2 mu
=
3
m
2
w
−−
u
1
w
=
u
12
2(b)[5]
Use of I
=
−
for P or
mv mu
equivalent
EITHER: (see diagram)
7
mu
u
−
=
−
7
m
ku
2
12
7
mu
6
mu
or
7
mku
−
3
mu
=
+
12
12
OR: (see diagram)
7
mu
u
(
)
=
7
m
−−
ku
2
12
or
−
7
mu
6
mu
−
=
+
7
mku
3
mu
12
12
7
EITHER:
k =
12
Use of I
=
mv mu
−
for P or
equivalent
5
OR:
k =
12
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