- Aug 9, 2000
- 18,378
- 2
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Web assign is teh worst thing to happen to me in college
They give around 12 problems a week and it takes me atleast a total of six hours to get through it I like the idea of it, but it is stupid because they do not tell you what you did if you got the problem wrong. Can you guys help me? I am on my last submission.
A uniform stick 1.5 m long with a total mass of 300 g is pivoted at its center. A 2.0 g bullet is shot through the stick midway between the pivot and one end .The bullet approaches at 250 m/s and leaves at 160 m/s. With what angular speed is the stick spinning after the collision?
I thought that this involved angular momentum, but the I saw that it could be like a pendulem problem, so i used Kenetic energy. KE=.5Iw^2. (I=moment of inertia, w=angualr velocity). Here is what I did. .5mv^2+0=.5Iw^2+.5mv^2. plug in the numbers....I get 41.83. It's wrong. Did I calculate inertia wrong? Here is how i calculated it...I (for rod with middle pivot)=.5mr^2. the bullet hits the raduis at the midpoint between teh pivot and the end, therefore the radius is .375 since you have to divide the rod by four.
I just want you guys to check this last one, I think i got it.
A.person of mass 55 kg stands at the center of a rotating merry-go-round platform of radius 3.5 m and moment of inertia 670 kg · m2. The platform rotates without friction with angular velocity 1.5 rad/s. The person walks radially to the edge of the platform.
(a) Calculate the angular velocity when the person reaches the edge.
ans .7479069767
Calculate the rotational kinetic energy of the system of platform plus person before the person's walk.
ans 753.75
Calculate the rotational kinetic energy of the system of platform plus person after the person's walk.
ans 375.8
They give around 12 problems a week and it takes me atleast a total of six hours to get through it I like the idea of it, but it is stupid because they do not tell you what you did if you got the problem wrong. Can you guys help me? I am on my last submission.A uniform stick 1.5 m long with a total mass of 300 g is pivoted at its center. A 2.0 g bullet is shot through the stick midway between the pivot and one end .The bullet approaches at 250 m/s and leaves at 160 m/s. With what angular speed is the stick spinning after the collision?
I thought that this involved angular momentum, but the I saw that it could be like a pendulem problem, so i used Kenetic energy. KE=.5Iw^2. (I=moment of inertia, w=angualr velocity). Here is what I did. .5mv^2+0=.5Iw^2+.5mv^2. plug in the numbers....I get 41.83. It's wrong. Did I calculate inertia wrong? Here is how i calculated it...I (for rod with middle pivot)=.5mr^2. the bullet hits the raduis at the midpoint between teh pivot and the end, therefore the radius is .375 since you have to divide the rod by four.
I just want you guys to check this last one, I think i got it.
A.person of mass 55 kg stands at the center of a rotating merry-go-round platform of radius 3.5 m and moment of inertia 670 kg · m2. The platform rotates without friction with angular velocity 1.5 rad/s. The person walks radially to the edge of the platform.
(a) Calculate the angular velocity when the person reaches the edge.
ans .7479069767
Calculate the rotational kinetic energy of the system of platform plus person before the person's walk.
ans 753.75
Calculate the rotational kinetic energy of the system of platform plus person after the person's walk.
ans 375.8
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