A ball with a mass of 2 kg2kg moving at 16 m/s16ms hits a still ball with a mass of 21 kg21kg. If the first ball stops moving, how fast is the second ball moving? How much kinetic energy was lost as heat in the collision?

1 Answer
Oct 28, 2016

In the first scenario, momentum conservation law will be applied.

Explanation:

from the law,
m_1u_1+m_2u_2=m_1v_1+m_2v_2m1u1+m2u2=m1v1+m2v2

here,
m_1=2kgm1=2kg
m_2=21kgm2=21kg
u_1=16ms^(-1)u1=16ms1
u_2=0ms^(-1)u2=0ms1
v_1=0ms^(-1)v1=0ms1
we have to find v_2v2
if we put all the values in the equation, we will find,

2*16+21*0=2*0+21*v_2216+210=20+21v2
or, 32=21v_2or,32=21v2
or, v_2=32/21or,v2=3221
or, v_2=1.524ms^(-1)or,v2=1.524ms1

for the energy loss,
E_(i)=1/2*2*16^2+1/2*21*0^2Ei=122162+122102
=256j=256j

E_(f)=1/2*2*0^2+1/2*21*1.524^2Ef=12202+12211.5242
=24.387j=24.387j

so, Delta E=E_(i)-E_f
=256j-24.387j
=231.613j