Question

Two objects of mases 100g and 200g are moving alongthe same line & with velocity of2 m/s& 1m/s respectively. they collide & afterthe collision the first object moves at a velocity of 1.67m/s. find velocity of 2 nd object...... plz fast i m in need for class9

Answer 1

Momentum of first object: 0.1kg x 2 m/s = 0.2 kg m/s

Momentum of second object: 0.2 kg x 1 m/s = 0.2 kg m/s

Total Momentum: 0.2 + 0.2 = 0.4 kg m/s

AFTER COLLISION
Momentum of first object: 0.1 kg x 1.67 m/s
= 0.167 kg m/s

Momentum of second object: 0.2 kg x V (Final Velocity is not known ) = 0.2V

Total Momentum: 0.167 + 0.2V
According to Law of conservation of momentum
0.4 = 0.167+0.2V
0.4 - 0.167 = 0.2V
0.233 = 0.2V
V = 0.233÷0.2
V = 1.165 m/s
Velocity of second object is 1.165 m/s

Answer 2

for the 1st obj we hve;
M=100g=0.1 kg
V=2 m/s
P=M x V
i.e.=0.1 x 2
     =0.2 kg.m/s

for the 2nd obj we hve;
M=200g
V=1 m/s
P=M x V
i.e.=0.2 x 1= 0.2 kg.m/s

total (P) before collision=0.2 + 0.2
                                      =0.4 kg.m/s

aft collision, first obj's;
M=100g = 0.1kg
V=1.67 m\s
P= M x v 
i.e.= 0.1 x 1.67
     = 0.167 kg.m\s

2nd obj's; 
M= 0.2 kg
V= v       (let us consider)
P= 0.2v kg.m/s

=Now, according to the newton's law of conservation of momentum;
total momentum bef. collidion = total momentum aft. collision
      i.e. (0.2 + 0.2) kg.m/s        = (0.2 v +0.167) kg.m\s
             0.4                 =    0.2 v + 0.167
              0.4 - 0.167    =    0.2v
              0.163            = 0.2 v 
                   v  = 0.163 ÷ 0.2
                       = the value of v