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Physics Problems
發問:
1. A spider crawling across a table leaps onto a magazine blocking its path. The initial velocity of the spider is 0.890 m/s at an angle of 36.5° above the table, and it lands on the magazine 0.0730 s after leaving the table. Ignore air resistance. How thick is the magazine? Express your answer in millimeters.... 顯示更多 1. A spider crawling across a table leaps onto a magazine blocking its path. The initial velocity of the spider is 0.890 m/s at an angle of 36.5° above the table, and it lands on the magazine 0.0730 s after leaving the table. Ignore air resistance. How thick is the magazine? Express your answer in millimeters. 2. The 1994 Winter Olympics included the aerials competition in skiing. In this event skiers speed down a ramp that slopes sharply upward at the end. The sharp upward slope launches them into the air, where they perform acrobatic maneuvers. In the women's competition, the end of a typical launch ramp is directed 61° above the horizontal. With this launch angle, a skier attains a height of 15 m above the end of the ramp. What is the skier's launch speed?
最佳解答:
1. Consider the vertical motion of the spiderUsing equation of motion: s = ut + (1/2).a.t^2with u = 0.89.sin(36.5) m/s = 0.529 m/s, a = -g(=-10 m/s2)t = 0.073 s, s = thickness of magazinehence, s = [0.529 x 0.073 + (1/2).(-10).(0.073)^2] m i.e. s = 0.012 m = 12 mm 2. Consider the vertical motion of the skier. Use equation of motion: v^2 = u^2 + 2.a.s with v = 0 m/s, u =?, s = 15 m, a = -g(=-10 m/s2) hence, 0 = u^2 + 2.(-10).(15) i.e. u = square-root[2 x 10 x 15] m/s = 17.32 m/s Hence, velocity of skier on leaving the ramp = 17.32/sin(61) m/s = 19.8 m/s
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