A car of mass m moving at a speed v1 collides and couples with the back of a truck of mass 3m moving initially in the same direction as the car at a lower speed v2. (Use any variable or symbol stated above as necessary.)

(b) What is the change in kinetic energy of the car–truck system in the collision?

  1. 👍
  2. 👎
  3. 👁
  1. initial momentum = m V1 + 3m V2
    final momentum = 4 m V3
    same final momentum as initial
    V3 = (V1+3 V2)/4

    initial Ke = .5 m( V1^2 + 3 V2^2)

    final Ke = .5 (4m) (V3^2) = 2 m(V3^2) = 4 (.5m)V3^2

    so change = .5m (V1^2+3V2^2 - 4 V3^2)
    V3^2 = (V1^2 + 6V1V2 + 9V2^2)/16
    4 V3^2 = (V1^2 + 6V1V2 + 9V2^2)/4
    so change =
    (1/2) m( (3/4)V1^2 -6/4 V1V2 +(3/4)V2^2)

    = (m/8) (3 V1^2 - 6 V1V2 + 3 V2^2)

    = (3 m/8)(V1-V2)^2

    1. 👍
    2. 👎
    It came out awful coincidental though.

    1. 👍
    2. 👎
  3. i cant seem to find the error but i still cant get the correct answer

    1. 👍
    2. 👎
  4. Do it all over very carefully is all I can suggest.

    1. 👍
    2. 👎
  5. You forgot the negative at the beginning in part B. Everything else is correct

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Physics

    A car of mass 600 kg is moving at a speed of 20 m/ collides with a stationary car of mass 900 kg.if the first car bounces back at 4 m/s,at what speed does the second car move after the collusion?

  2. physics

    A 2,200-kg car moving east at 10.0 m/s collides with a 3,000-kg car moving north. The cars stick together and move as a unit after the collision, at an angle of 35.0° north of east and at a speed of 5.16 m/s. Find the speed of

  3. physics

    A railroad car of mass 2.15 ✕ 104 kg moving at 3.15 m/s collides and couples with two coupled railroad cars, each of the same mass as the single car and moving in the same direction at 1.20 m/s. (a) What is the speed of the

  4. physics

    several students are riding in bumper cars at an amusement park. the combined mass of a car A and its occupants is 250 kg. the combined mass of car B and its occupants is 200 kg. Car A is 15 m away from car B and moving to the

  1. Physics

    A snooker ball with a mass of 0.3kg moving at 2.5m/s collides with another ball of 0.2kg mass and moving in the same direction with a speed of 1.20m/s . Assuming the collision is elastic, calculate the speed and direction of each

  2. Physics

    A car mass 600kg moving a speed 20m/ collides with a stationary car mass 900kg.if the first car bounce back 4m/s.what speed does the second object after collision

  3. Physics

    An 800kg car moving at 80kmh^-1 collides with a 1200kg car moving at 40kmh^-1 in the same direction. If the car sticks together, calculate their common speed

  4. physics..please help?

    At rest, a car’s horn sound at the note A(440Hz) The horn is sounded while the car is moving down the street. A bicyclist moving the same direction with one third the car’s speed hears a frequency of 415 Hz. What is the speed

  1. physics

    a 2kg car moving towards the right at 4 m/s collides head on with a 8 kg car moving towards the left at 2 m/s and they stick together. After the collision, the velocity of the combined boides is

  2. physics

    A Truck moving West at a velocity of 43 m/s collides with a stationary car with exactly 1/5 of its mass. is there two vehicles all together, calculate the magnitude of the velocity of the combined mass immediately after collision


    1. A 4.0 N force acts for 3 seconds on an object. The force suddenly increases to 15 N and acts for one more second. What impulse was imparted by these forces to the object? 2. A railroad freight car, mass 15,000 kg, is allowed to

  4. Physics

    A railroad car with a mass of 12400 kg collides and couples with a second car of mass 18700 kg that is initially at rest. The first car is moving with a speed of 7.7 m/s prior to the collision. (a) What is the initial momentum of

You can view more similar questions or ask a new question.