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DLS
Group Title
At the same instant that a 0.50kg ball is dropped from 25 m above Earth, a second ball, with a
mass of 0.25 kg, is thrown straight upward from Earth’s surface with an initial speed of 15 m/s.
They move along nearby lines and pass without colliding. At the end of 2.0 s the velocity of
the center of mass of the twoball system is:
 one year ago
 one year ago
DLS Group Title
At the same instant that a 0.50kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth’s surface with an initial speed of 15 m/s. They move along nearby lines and pass without colliding. At the end of 2.0 s the velocity of the center of mass of the twoball system is:
 one year ago
 one year ago

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mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
options??
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
A. 11 m/s, down B. 11 m/s, up C. 15 m/s, down D. 15 m/s, up E. 20 m/s, down
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
V(a)=20m/s V(b)=5m/s
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
Since this is multiple choice, lets use 10 m/s^2 as the acceleration due to gravity.
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
so 0.50*20+0.25*(5)/0.75
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
The trick is to look at the momentum of the system after 2 seconds. So for the heavy ball, after two seconds, it has a velocity of 20 m/s.
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
10+1.25/0.75 (wil we have a minus sign or are we considering just the mag?
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
Thus it has a momentum of 10 kg*m/s.
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
u took downwards negative?
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
yaa, i took downwards negative. The light ball will have a velocity of 5 m/s (15 m/s going up minus 20 m/s due to gravity gives 5 m/s downward). So it has a momentum of 1.25 kg*m/s.
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
In both cases, the negative sign indicates the momentum is downward, and the sum is 11.25 kg*m/s.
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
Find the velocity of the system by dividing by the total mass (0.75 kg)?? then solve it and you get your answer.
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
i took downwards positive and upwards negative,im getting something different
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
no, always took downwards negative and upwards positive
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
v=0+10*2 v=20m/s downwards and v=1520 v=5m/s upwards
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
no!!!!
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
Find the velocity of the system by dividing by the total mass (0.75 kg) and you get 15 m/s down. so your answer is option C) 15 m/s up.
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
wait u messed up!!
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
no,, 15 m/s down.
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
im taking downwards negative and upwards positive so for the 0.25 kg ball, v=15+20=35? we are taking upwards positive right
 one year ago

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
right
 one year ago

DLS Group TitleBest ResponseYou've already chosen the best response.1
11.25/0.75=15m/s
 one year ago
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