1.7 m = longer blue arrow 1.35 m = short blue arrrow 30 degrees = angle above th

Question

1.7 m = longer blue arrow    1.35 m = short blue arrrow 30 degrees = angle above the end of the short blue arrow

Question:

1. A shop sign weighing 215 N is supported by a uniform 135-N beam shown in the figure above. Find the tension in the guy wire and the horizontal and the vertical forces exerted by the pin on the beam.

2.       A beam balances 30.0 cm from one end. When a 0.75 kg mass is hung from that end, the balance point moves 8.0 cm toward that end. Find the mass of the beam.

3.       A 1.0-m radius flywheel is to be made from steel in the form of a solid disc. If the flywheel when turning at 60 rpm store as much energy as a 100-W lamp uses in one minute, how thick must the flywheel be if the density of steel is 7880 kg.m-3.

Explanation / Answer

No figure is attached for part 1 and 2

Part 3

Energy consumed by 100 W lamp in 1 minute

E = P*t = 100*60 = 6000 J

now energy of flywheel

E' =1/2 * I*w^2

w = 60rpm = 60*2*3.14/60 = 6.28 rad/s

for disc I = MR^2/2

E' = 1/2*MR^2/2 * 6.28*6.28

E' = 9.85M

now E= E'

6000=9.85M

M = 608kg

Let thickness of flywheel is t then

volume = pi*R^2*t

mass M = volume *density

608 = 3.14*1*1* t *7880

t = 0.0245m

or

t = 2.45cm

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