In the chapter, we saw that a person’s reaction time is generally not quick enou

Question

In the chapter, we saw that a person’s reaction time is generally not quick enough to allow them to catch a dollar bill dropped between the fingers. A demonstration of reaction time is to hold one end of a dollar bill so that it hangs lengthwise below your fingers, then ask a friend to hold his fingers near the lower corner of the bill. When you release the bill, he is to try to catch it. Part A If a typical reaction time in this case is 0.25 s, how long would a bill need to be for a person to have a good chance of catching it?

Explanation / Answer

We need to calculate how far an object falls in 0.25 seconds of free fall.

using kinematics equation for free fall

S = ut + 0.5*a*t^2

u =0 and a = 9.81 m/sec^2

S = 0*t + 0.5*9.81*0.25^2 = 0.30656 m = 30.656 cm

Bill should be 30.656 cm long to be for a person to have a good chance of catching it.

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