8/13/2019 EGR280 Mechanics 18 ImpulseMomentumRB

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EGR 280 Mechanics Problem Set 18

Graphics and problem statements 2004 R.C. Hibbeler.Published by Pearson Education, Inc., Upper Saddle River, NJ.

18.1 The man pulls the rope off the reel with a

constant force of 8 lb in the direction shown. If the

reel has a weight of 250 lb and a radius of gyration

kA= 0.8 ft, determine the angular elocity of thereel in ! s starting from rest. "eglect friction and

the weight of rope remoed.

Ans: # = $.0% rad&s

18.2 The drum has a mass of '0 (g, a radius of!00 mm and radius of gyration kO= )25 mm. If

*s= 0.% and *(= 0.!, determine the drum+s angular

elocity 2 s after it is released from rest. Ta(e =!0-.

Ans: # = 2'. rad&s

18.3 The crate has a mass mc. /etermine theconstant speed voit acuires as it moes down the

coneyor. Treat the rollers as thin rings with hae

mass m, radius rand spaced dapart. "ote that

friction causes each roller to rotate when the cratecomes in contact with it.

Ans: v02= 12gdmc/m sin

18.4 The man sits on the swiel chair holding two53lb weights with his arms outstretched. If he is

turning at ! rad&s in this position, determine his

angular elocity when the weights are drawn in

and held 0.! ft from the a4is of rotation. ssumehe weighs )$0 lb and has a radius of gyration of

kz=0.55 ft about the 63a4is. "eglect the mass of his

arms and the si6e of the weights.

Ans: # = $.'5 rad&s

8/13/2019 EGR280 Mechanics 18 ImpulseMomentumRB

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18.5 thin ring haing a mass of )5 (g stri(es the

203mm high step. /etermine the minimumangular elocity #)the ring can hae so that it will

7ust roll oer the step atAwhen it stri(es it.

Ans: #)= 2.$0$ rad&s

18.6 The $3lb slender rodABis originally at rest,

suspended in the ertical position. )3lb ball is

thrown at the rod with a elocity v= 50 ft&s andstri(es the rod at C. /etermine the angular

elocity of the rod 7ust after the impact. et e=

0.' andd= 2 ft.

Ans: #2 = 5.2! rad&s