1. You are on roller skates and coasting (i.e. moving at a constant speed) on a
ID: 1570291 • Letter: 1
Question
1. You are on roller skates and coasting (i.e. moving at a constant speed) on a long and straight driveway when you see Tom your six-year old brother standing still and watching nearby. Tom weighs half as much as you do. When the two of you are abreast of each other you grab Tom, lifting him into your arms. What will happen to you?
2. You are next to a frozen lake and wish to reach the opposite shore. You are not certain of the thickness of the ice and whether it will absolutely support your weight without cracking and dumping you into the icy water below it. You wish to take the least amount of risk. Based on your understanding of Physics, which one of the following actions would you take?
Explanation / Answer
In the first part using conservation of momentum
MV + 0 = (M+M/2)Vf
Thus Vf = 2/3 V
Hence speed of men will decrease.
Second part : for minimum risk one should use the method so that pressure on the ice decreases thus if the person will lie horizontally on ice so the area of contact will increase and thus pressure will decrease and thus slowly by slipping men can go to another side.
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