CAIE A-Level Physics 3.3.2 Applying Conservation of Momentum

Practise solving one- and two-dimensional collisions, recoil and decay using vector momentum conservation.

[Maximum number: 3]

Two blocks travel directly towards each other along a horizontal, frictionless surface. The blocks collide, as illustrated in Fig. 3.1.

Fig. 3.1

Block A has mass 3 M and block B has mass M.
Before the collision, block A moves to the right with speed $0.40 \mathrm{~ms}^{-1}$ and block B moves to the left with speed $0.25 \mathrm{~ms}^{-1}$ .
After the collision, block A moves to the right with speed $0.20 \mathrm{~m} \mathrm{~s}^{-1}$ and block B moves to the right with speed v.

Determine speed v.

p=m v or $3 M \times 0.40$ or $M \times 0.25$ or $3 M \times 0.2$ or M v

C1

$(3 M \times 0.40)-(M \times 0.25)=(3 M \times 0.2)+M v$

C1

$\begin{aligned} v =(3 \times 0.40)-0.25-(3 \times 0.2) =0.35 \mathrm{~m} \mathrm{~s}^{-1} \end{aligned}$

A1

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3.3.2—The principle of conservation of momentum to solve simple problems question 1