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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:
 2 years ago
 2 years 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:
 2 years ago
 2 years ago

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

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

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

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

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

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

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

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

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

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

mayankdevnani Group TitleBest ResponseYou've already chosen the best response.1
right
 2 years ago

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