M = mass of the first sphere = 10 kg
m = mass of the second sphere = 8 kg
V = initial velocity of the first sphere before collision = 10 m/s
v = initial velocity of the second sphere before collision = 0 m/s
V' = final velocity of the first sphere after collision = ?
v' = final velocity of the second sphere after collision = 4 m/s
using conservation of momentum
M V + m v = M V' + m v'
(10) (10) + (8) (0) = (10) V' + (8) (4)
100 = (10) V' + 32
(10) V' = 68
V' = 6.8 m/s
Answer:
Time taken by A and B is 1.2 hr.
Explanation:
Given that
Time taken by tank when all(A+B+C) are open = 1 hr
Time taken by tank when A+C are open = 1.5 hr
Time taken by tank when B+C are open = 2 hr
If we treat as filling of tank is a work then
Work = time x rate
Lets take work is 1 unit
1 = 1(1/a+1/b+1/c) ---------1
1 = 1.5(1/a+1/c) ----------2
1 = 2(1/b+1/c) --------3
From equation 1 and 3
1=1(1/a+1/2)
a=2
Form equation 2
1 = 1.5(1/2+1/c)
c=6
From equation 3
1 = 2(1/b+1/6)
b=3
So time taken by
A is alone to fill tank is 2 hr
B is alone to fill tank is 3 hr
C is alone to fill tank is 6 hr
So 
Time taken by A and B is 1.2 hr.
Answer:
A
Explanation:
sound waves hit the canyon walls, then bounce back towards you. That's why you hear an echo