f6 phy circular motion......

紫魂

2011-05-12 2:33 am

1. A racing car of mass 500kg goes around acircular racetrack with a diameter of 350m at a speed of 150km h^-1. What isthe centripetal force acting on the car?
Ans:2500N
點解我將150kmh^-1變做150000m/3600s,再代入其他數入F=mv^2/r
都計唔到答案….除非個diameter=350m當係r……定係答案係錯?

2. A circular space station of radius 1000m is designed to rotate about an axisthrough its centre to simulate gravity. How many revolutions per minute must itperform in order to produce an artificial gravity of 9.80ms^-2?
Ans:0.95rev min^-1

3. A ceiling fan is turning at a rate of 100 revolutions per minute. A spideris clinging to a blade of the fan. If the spider experiences a centripetal accelerationgreater than 0.3g, it will lose its grip on the blade and be flung off. How farfrom the centre of the fan can the spider safely go?
Ans:1.05m
我唔明佢咩意思……

回答 (1)

天同

2011-05-12 4:15 am

✔ 最佳答案

1. I think the answer is wrong. The correct answer should be 5000 N
2. Centripetal acceleration = 1000w^2
where w is the nagular velocity of the space station
hence, 1000w^2 = 9.8
w = 0.1 s^-1
hence, no of revolution per minute = (0.1/2.pi) x 60 = 0.955

3. Let R be the distance from the centre of the fan,
centripetal acceleration experienced by the spider
= R.(100 x 2.pi/60)^2

Hnece, 0.3g = R.(100 x 2.pi/60)^2
solve for R gives R = 0.027 m
[Your answer seems not correct]

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