CBSE Class 11-science Answered

Dear Student

Girl wight =  45 kg

Plank weight= 150 Kg

Velocity of girl relative to plank v1 = 1.5 m/s

Velocity of plank = v2

Consider the conser vation of momentum

Momentum of he girl  P1 = mv=45X1.5 = 67.5 kg m/s

Say momentum of plank = P2 = mv= 150 v2

For conservation of momentum P1+P2  =0

==>  P2= 150 v2=  -P1= - 67.5 

==>  v2=  67.5/150 = - 0.45 m/s

"-" denotes that the velocity of plank is in opposite direction to girl's movement direction.

a)  Girl's speed relative to ice=  v1+v1 = 1.5- 0.45 = 1.05 m/s

b) The velocity of plank we were talking above is the Speed of plank relative to ice = 0.45 m/s

Regards

Team

Topperlearniong