A skittle is a wooden object that can stand upright on one end. In a game of Skittles, a ball is thrown at some skittles to knock them over, as shown. (Source: © CMBiles/Getty Images) The diagram below shows the ball just before it collides with a skittle. The ball is thrown again, and collides with another stationary skittle. During the collision the horizontal velocity of the ball changes from $$\(7.2 \mathrm{~ms}^{-1}\)$$ to $$\(1.6 \mathrm{~ms}^{-1}\)$$. The horizontal velocity of the skittle immediately after the collision is $$\(3.1 \mathrm{~ms}^{-1}\)$$ in the same direction as the ball. Determine the mass of the ball. mass of skittle $$\(=1.4 \mathrm{~kg}\)$$ (3) .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. Mass of ball $$\(=\)$$ ...................................................
Exam No：wph11-01-que-20240112 Year：2024 Question No：16(c)
Answer:
Use of \(p=m v\)
Use of total momentum before collision = total momentum after collision
Mass of ball \(=0.78 \mathrm{~kg}\)
Example of calculation
\[
\begin{array}{l}
m \times 7.2 \mathrm{~m} \mathrm{~s}^{-1}=m \times 1.6 \mathrm{~m} \mathrm{~s}^{-1}+1.4 \mathrm{~kg} \times 3.1 \mathrm{~m} \mathrm{~s}^{-1} \\
m=\frac{1.4 \mathrm{~kg} \times 3.1 \mathrm{~m} \mathrm{~s}^{-1}}{7.2 \mathrm{~m} \mathrm{~s}^{-1}-1.6 \mathrm{~m} \mathrm{~s}^{-1}}=0.775 \mathrm{~kg}
\end{array}
\]
Use of total momentum before collision = total momentum after collision
Mass of ball \(=0.78 \mathrm{~kg}\)
Example of calculation
\[
\begin{array}{l}
m \times 7.2 \mathrm{~m} \mathrm{~s}^{-1}=m \times 1.6 \mathrm{~m} \mathrm{~s}^{-1}+1.4 \mathrm{~kg} \times 3.1 \mathrm{~m} \mathrm{~s}^{-1} \\
m=\frac{1.4 \mathrm{~kg} \times 3.1 \mathrm{~m} \mathrm{~s}^{-1}}{7.2 \mathrm{~m} \mathrm{~s}^{-1}-1.6 \mathrm{~m} \mathrm{~s}^{-1}}=0.775 \mathrm{~kg}
\end{array}
\]
Knowledge points:
CH1 - Mechanics
Solution:
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