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Question: A 250 g grass hopper moving due south at 20 cms<sup>-1</sup> (at mid air) collides with 150 g grassh...

A 250 g grass hopper moving due south at 20 cms-1 (at mid air) collides with 150 g grasshopper moving 60 cms-1 due north. Find the decrease in KE if they move together after collision.

A

0.3 J

B

3.0 J

C

0.03 J

D

0.003 J

Answer

0.03 J

Explanation

Solution

∆KE = m1m22(m1+m2)(v1−v2)2\frac{m_{1}m_{2}}{2\left( m_{1} + m_{2} \right)}\left( v_{1} - v_{2} \right)^{2}

= 0.25×0.15(0.8)22(0.4)=0.03\frac{0.25 \times 0.15(0.8)^{2}}{2(0.4)} = 0.03