A ball with a mass of #2 kg# moving at #16 m/s# hits a still ball with a mass of #21 kg#. 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

Answer:

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_2#

here,
#m_1=2kg#
#m_2=21kg#
#u_1=16ms^(-1)#
#u_2=0ms^(-1)#
#v_1=0ms^(-1)#
we have to find #v_2#
if we put all the values in the equation, we will find,

#2*16+21*0=2*0+21*v_2#
#or, 32=21v_2#
#or, v_2=32/21#
#or, v_2=1.524ms^(-1)#

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

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

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