A ball with a mass of #8 kg# moving at #3 m/s# hits a still ball with a mass of #15 kg#. If the first ball stops moving, how fast is the second ball moving?

Question

A ball with a mass of #8 kg# moving at #3 m/s# hits a still ball with a mass of #15 kg#.  If the first ball stops moving, how fast is the second ball moving?

Isabella Alvarez · Accepted Answer

The velocity of the second ball after the collision is #=1.6ms^-1#

We have conservation of momentum

#m_1u_1+m_2u_2=m_1v_1+m_2v_2#

The mass the first ball is #m_1=8kg#

The velocity of the first ball before the collision is #u_1=3ms^-1#

The mass of the second ball is #m_2=15kg#

The velocity of the second ball before the collision is #u_2=0ms^-1#

The velocity of the first ball after the collision is #v_1=0ms^-1#

Therefore,

#8*3+15*0=8*0+15*v_2#

#15v_2=24#

#v_2=24/15=1.6ms^-1#

The velocity of the second ball after the collision is #v_2=1.6ms^-1#

Lily Adams · Answer

#1.6\ ext{ m/s}# The linear momentum in a collision always remains conserved irrespective of type of collision elastic or inelastic. If #v_1=0# & #v_2# are the velocities of balls of masses #m_1=8\ kg# & #m_2=15\ kg# moving with initial velocities #u_1=3\ m/s# & #u_2=0# respectively, after collision then by the conservation of linear momentum, we have #m_1u_1+m_2u_2=m_1v_1+m_2v_2# #8(3)+15(0)=8(0)+15v_2# #24=15v_2# #v_2=24/15# #v_2=1.6\ ext{ m/s}# hence, the velocity of second ball, after collision, is #1.6# m/s

Nora Arzate · Answer

undefined The second ball will move at a speed of 1.6 m/s.