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I WILL lifesaver 1. Consider a point moving at a constant speed v on a circle of

ID: 2022918 • Letter: I

Question

I WILL lifesaver

1. Consider a point moving at a constant speed v on a circle of radius r. What is the
relation between v, r, and the rotation frequency, f ?

2. Show that the centripetal acceleration relation, ac = v2/r, can be put into the form
ac = [2f]2·r.

3. In this experiment you will determine g from experimental values of m1, M2, r,
and f. The frequency f is found by dividing the number of revolutions by the time
for those revolutions. Assume g = 9.80 m/s2, take m1 = 500 g, M2 = 800 g, and r =
18 cm, and calculate the frequency f, and then the time for 50 cycles.

4.) Referring to the equation g = m1· [2f]2·r/M2., what do you expect the frequency to vary with the radius of the rotational motion?

Explanation / Answer

1) f -> no of rotations in 1 sec =1/time for one rotation = 1/(2r/v) = v/2r

2) v2/r = (2rf)2 /r = (2f)2 . r

3) g = m1 [2f]2·r/M2 => f=1/2 * (g.M2/M1.r) = 1.4855

=> time for 1 cycle =1/f =0.6372

=> time for 50 cycle =50/f =50*0.6372 =33.66 sec

4) f is proportional to 1/r