F.4 Physics (有圖解,要步驟)!!!

2010-12-28 1:59 am

An object of mass 1 kg is hung by a spring balance inside a box. The figure shows the whole set-up which is placed on the ground. It is known that the mass of the set-up is 5 kg.The box is then dropped from a height to the ground.

圖片參考：http://imgcld.yimg.com/8/n/HA00005851/o/701012270097913873432160.jpg

1. What is the weight of the object?2. If air resistance is ignored, what is the acceleration of the box as it falls?3. If air resistance should be taken into consideration, how will it affect the acceleration of the box?4. It is found that the box finally falls with a constant speed.
(a) Explain why this happens.
(b) What is the air resistance when this happens?5. What is the reading of the spring balance when the set-up accelerates in the mid-air? Explain your answers briefly.

回答 (1)

天同

2010-12-28 3:46 am

✔ 最佳答案

1. The weight is the object = 1g N, where g is the acceleration due to gravity.If g is taken to be 10 m/s2, weight of the object = 10 N2. The acceleration of the box = g m/s2 = 10 m/s23. The acceleration is reduced.4.(a) WHen the air resistance equals to the weight of the box, there is no net force acting. The box then falls with a constant speed.(b) The air resistance equals to the weight of the box, which is 5g N (=50 N)5. Since the whole set up is at free fall, the object experiences weightlessness. The reading on the spring balance is zero.

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