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A solid sphere with a diameter of 0.17 m is released from
Chapter 10, Problem 111GP(choose chapter or problem)
A solid sphere with a diameter of 0.17 m is released from rest; it then rolls without slipping down a ramp, dropping through a vertical height of 0.61 m. The ball leaves the bottom of the ramp, which is 1.22 m above the floor, moving horizontally (Figure 10–30). (a) Through what horizontal distance d does the ball move before landing? (b) How many revolutions does the ball make during its fall? (c) If the ramp were to be made frictionless, would the distance d increase, decrease, or stay the same? Explain.
Questions & Answers
QUESTION:
A solid sphere with a diameter of 0.17 m is released from rest; it then rolls without slipping down a ramp, dropping through a vertical height of 0.61 m. The ball leaves the bottom of the ramp, which is 1.22 m above the floor, moving horizontally (Figure 10–30). (a) Through what horizontal distance d does the ball move before landing? (b) How many revolutions does the ball make during its fall? (c) If the ramp were to be made frictionless, would the distance d increase, decrease, or stay the same? Explain.
ANSWER:
Step 1 of 3
Part a
We are required to calculate the horizontal distance d by which the ball moves. To calculate the horizontal distance, we need to calculate the linear speed and time considering the linear motion.
Let m be the mass of the sphere.
Using the conservation of mechanical energy principle (Equation 1),
\(mgh=\frac{1}{2} m v^{2}+\frac{1}{2} I \omega^{2}\)
where \(v\) is the speed achieved by the ball, \(I\) is the moment of inertia and \(\omega\) is the angular speed.
Given:
\(\text { Diameter of the sphere }=0.17 \mathrm{~m}\)
\(\text { Radius of the sphere } r=0.085 \mathrm{~m}\)
The moment of inertia of a sphere is
\(I=\frac{2}{5} m r^{2}\)
Height \(h=0.61 \mathrm{~m}\)
Substitute in equation (1),
\(\begin{array}{l} 9.81 \times 0.61 m=\frac{1}{2} m v^{2}+\frac{1}{2} \times \frac{2}{5} m r^{2} \times \frac{v^{2}}{r^{2}} \\ 5.98=\frac{1}{2} v^{2}+\frac{1}{5} v^{2} \\ v=2.92 \mathrm{~m} / \mathrm{s} \end{array}\)
For a vertical height \(h_{1}=\frac{1}{2} g t^{2}\)
\(\begin{array}{l} t=\sqrt{\frac{2 h}{g}} \\ t=\sqrt{\frac{2 \times 1.22}{9.81}} \\ t=0.5 \mathrm{~s} \end{array}\)
s (the height now is 1.22 m)
Therefore, the horizontal distance \(d=2.92 \times 0.5 \mathrm{~m}\)
\(d \approx 1.5 \mathrm{~m}\)
The required horizontal distance is 1.5 m.