I'd guess at valve B. more information about the interesting question would help.
Answer:
a. 250kg I think it's the right answer. hope it helps:)
The first one is dependent variable
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Answer:
Given: mass 1200kg
initial velocity: 4m/s
finial velocity: 10 m/s
time 3 sec
then
speed; initial velocity + final velocity/2
4+10/3
: 4.66m/s2
Answer:
Part a)

Part b)

Explanation:
Part a)
As we know that both charge particles will exert equal and opposite force on each other
so here the force on both the charges will be equal in magnitude
so we will have

here we have

now we have

Part b)
Now for the force between two charges we can say

now we have

now we have
