A barbell consists of a 500g ball and a 2.0 Kg ball connected by a massless 50 c
ID: 1610584 • Letter: A
Question
A barbell consists of a 500g ball and a 2.0 Kg ball connected by a massless 50 cm-long red Where is the center of mass X_cm with respect to the center of the heavier mass m? (a) 0.50 m (b) 0.40 m (c) 0.30 m (d) 0.20 m (e) 0.10 m (f) none of these What is the speed of the 20-Kg ball if they rotate about the center of mass at 40 rpm? (a) 41.9 m/s (b) 1.76 m/s (c) 0.42m/s (d) 0.04 m/s (e) none of these What is the speed of the 500-g ball if they rotate about the center of mass at 40 rpm? (a) 10.5 m/s (b) 702 m/s (c) 1.68 m/s (d) 0.67 m/s (e) none of these 8) Which will win the downhill race? Rank in order, from largest to smallest, the velocity of the objects in the figure: solid sphere (v_), solid cylinder (v_), thin hoop (v_). All objects have the same mass M and same radius R refer to the following roller coaster ride, which starts from rest at point A What is the point of the largest potential energy A) A B) B C) C D) D E) E What is the point of the largest kinetic energy A) A B) B C) C D) D E) E At which point the potential and kinetic energy would have about the same value A) A B) B C) C D) DExplanation / Answer
position of center of mass is
Xcm = m1 x1 + m2 x2/ m1 + m2
=0.5 (0) + 2 ( 0.5)/0.5+2
=0.4 m
(b)
v= rw = ( 0.5- 0.4) ( 4o rpm ( 2pi/60) = 0.42 m/s
(c)
v= 0.4 ( 4o rpm( 2pi/60) = 1.68 m/s
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8)
vcm =( 2gh/ 1+ I/ MR^2 )^1/2
moment of inertia of solid sphere 2/5 mR^2
vcm = ( 2gh/ 1 + 2/5 )^1/2
=( 2gh/1.4)^1/2
= ( 1.42gh)^1/2
moment of inertia of solid cylinder
I = MR^2/2
vcm = ( 2gh/ 1 + 1/2 )^1/2
=( 2gh/1.5)^1/2
moment of inertia of hoop
I = MR^2
vcm = ( 2gh/ 1 + 1 )^1/2
= ( 1gh)^1/2
v solid cylinder > v spherical > v hoop
As per guide line I worked first two problems
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