A skateboarder cruising across a smooth, level sidewalk is approaching a pipe gu
ID: 1781039 • Letter: A
Question
A skateboarder cruising across a smooth, level sidewalk is approaching a pipe guardrail. It seems like a good idea for him to jump over the rail and let the skateboard pass under the rail. The mass of the boy is 42.0 kg, the mass of the skateboard is 2.35 kg, the initial cruising speed is +5.57 m/s, and the instant after leaving contact with the board, the boy's velocity relative to the sidewalk is 5.86 m/s, 9.36° above the horizontal. If we ignore the force of friction between the skateboard and the sidewalk, determine the skateboard's velocity relative to the sidewalk at the instant the boy leaves the board.
Explanation / Answer
conserving the horizontal momentum,
(42 + 2.35) x 5.57 = 42 x 5.86 x cos9.36 + 2.35 x v
=> v = (247.0295 - 242.8431)/2.35 = 1.78143 m/s