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18.3: More Examples

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    Whiteboard Problem \(\PageIndex{1}\): Sliding Penguin


    Consider a penguin sitting on a ramp, as shown in the figure on the left. The ramp makes an angle of 15\(^\circ\) with respect to the floor, the mass of the penguin is 45 kg, and the coefficient of static friction between the penguin and the ramp is 0.20.

    1. In the figure on the left, will the penguin slide down the ramp or not?
    2. Now I tie a rope to the penguin, as shown in the figure on the right. This rope goes over a frictionless, massless pulley. How hard must I pull on the rope before the penguin just starts to move?


    Whiteboard Problem \(\PageIndex{2}\): Kinematics Review

    Two children are going to race their sleds across a frozen pond. They run towards the pond and jump onto the sleds, and race for a point 10 m away from their starting point. The first child has a mass of 40 kg, and his sled has a coefficient of friction of 0.023. The second child is less massive (35 kg), but her sled has a larger coefficient of friction, 0.035.

    1. Which child will win the race, assuming the only forces acting on them are gravity and the contact force between the ice and sleds?
    2. When whoever wins reaches the finish line, how far behind them is the other?
    3. What is each of their speeds at the end of the race?


    18.3: More Examples is shared under a CC BY-SA license and was authored, remixed, and/or curated by Christopher Duston, Merrimack College.

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