Question

a 5 kg body and 10 kg body approaches. each other at 21m/s . determine the speed after elastic collision

Answer 1

Answer:

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Let the velocities of 10kg & 20kg ball before collision are u1=20m/s(+X axis) & u2=−20m/s( -X axis) and after collision v1 & v2respectively. Than by the principal of momentum conservation: -

m1u1+m2u2=m1v1+m2v2

(10×20)+(20×(−20))=(10×v1)+(20×v2)

v1+2v2=−20 ---------------------(i) 

Since the collision is perfectly elastic (e = 1) 

e=(v2−v1)/(u1−u2)=1

v2−v1=20−(−20)=40------------------------(ii) 

On adding (i) & (ii): - 

3v2=20

44v2=6.67m/s