physics

posted by .

A 120 kg mass is blown apart into an 80 kg piece and 40 kg piece. after the blast, the two masses are moving apart with a relative velocity of 60 m/s. the total kinetic energy after the explosion is:
A. 21 kJ
B. 35 kJ
C. 48 kJ
D. 56 kJ
E. 82 kJ

Because of momentum conservation rules, the two pieces must go in opposite directions with
V2 = 2 V1
V1 is the final speed of the 80 kg piece; V2 is the final speed of the 40 kg piece.
Furthermore, because of the relative velocity that was given,and the opposite directions of motion,
V1 + V2 = 60 m/s
V1 + 2V1 = 60
V1 = 20 and V2 = 40 m/s
Now compute KE = (M1/2) V1^2 + (M2/2) V2^2
and see which answer is correct.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Physics

    A vessel at rest at the origin of an xy coordinate system explodes into three pieces. Just after the explosion, one piece, of mass m, moves with velocity (-30 m/s)i and a second piece, also of mass m, moves with velocity (-30 m/s)j. …
  2. physics

    A block of mass 7.33 kg in outerspace is moving at 1.72 m/s with no external forces acting on it. After an explosion, the block is split into two parts both having mass equal to half the mass of the original block. The explosion supplies …
  3. Physics

    Explosives are used to blow a rock apart. The explosion blows the rock into three fragments. Two fragments go off at a 76 degree angle to each other--a 6.2 kg piece at 26.7 m/s and a 5.5 kg piece at 23.3 m/s. Calculate the speed of …
  4. p

    An explosion breaks a 10 kg object (originally at rest) into two pieces, one of which is two times the mass of the other. If 8000 J is released in the explosion, a) how fast are the pieces moving away from their original location?
  5. physics

    a particle of mass 5m moving with speed v, explodes and splits into two pieces with masses of 2m and 3m. The lighter piece continues to move in the original direction with speed v relative to the heavier piece. What is the speed of …
  6. Physics

    A 6.2 kg model rocket is traveling horizontally and due south with a speed of 20.3 m/s when it explodes into two pieces. The velocity of one piece, with a mass of 1.6 kg, is v1 = (-12 m/s)i + (30 m/s)j + (15 m/s)k, with i pointing …
  7. Physics

    An explosion breaks an object into two pieces, one of which has 2 times the mass of the other. If 22500 J were released in the explosion, of which 21% is heat, how much kinetic energy did each piece acquire?
  8. physics

    A 2.40 kg firecracker explodes into two pieces and produces 170 J of heat, light, and sound energy. One of the pieces has a mass of 0.800 kg and a speed of 4.50 m/s after the explosion. If the mass of the other piece is 1.20 kg, what …
  9. Physics

    An explosion breaks an object initially at rest into two pieces, one of which has 2.0 times the mass of the other. If 7300 J of kinetic energy were released in the explosion, how much kinetic energy did the lighter piece acquire?
  10. physics

    An object initially at rest on a horizontal OX axis explodes into two pieces . One piece moves just after explosion along the axis OX with a speed of 6m/s. What are the direction and the magnitude of the velocity of the second piece …

More Similar Questions