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Title: What is the ratio of the final kinetic energy of the system to the initial kinetic energy? Post by: len5002 on Feb 13, 2013 Two objects moving with a speed v travel in opposite directions in a straight line. The objects stick together when they collide, and move with a speed of v/5 after the collision.
1.What is the ratio of the final kinetic energy of the system to the initial kinetic energy? Kf/Ki 2.What is the ratio of the mass of the more massive object to the mass of the less massive object? M/m Title: What is the ratio of the final kinetic energy of the system to the initial kinetic energy? Post by: Tony2001 on Feb 13, 2013 (M+m)*(v/5) = (M-m)*v or M + m = 5*M - 5*m 0r
4*M = 6*m or M = 1.5*m Answer for 2) Answer for 1 Final KE = 0.5*(2.5*m)*(v^2/25) and Initial KE = 0.5[1.5*mv^2 + m*v^2] Required Ratio = 1/25 = 0.04 Title: What is the ratio of the final kinetic energy of the system to the initial kinetic energy? Post by: tony3320 on Feb 13, 2013 The situation you describe is called an INELASTIC COLLISION. For inelastic collisions, momentum is conserved but kinetic energy is not. The best that can be said is that KEf will be less than KEi.
If you set the momentum before equal to the momentum after (the minus sign is because they are going towards each other) m1*v - m2*v = (m1+m2)*v/5 crunch through the math M1*v(1-1/5) = m2*v(1+1/5) then m1/m2 = 6/5*5/4 = 3/2 |