3 boxcars moving along frictionless track hits a motionless boxcar

In summary, the new speed of the four coupled boxcars after striking a motionless boxcar is 15m/s, as calculated using the third or second law of Newton and considering all boxcars to have the same mass.
  • #1
chaotiiic
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Homework Statement


Three boxcars are rolling along a virtually frictionless track at 20m/s when they strike another boxcar sitting motionless on the track. what is the new speed of the 4 coupled bovcars? all the boxcars have the same mass

Homework Equations


3rd or 2nd Newton law

The Attempt at a Solution


m_a(20) + m_b(20) + m_c(20) + m_d(0) = m_a(v_f) + m_b(v_f) + m_c(v_f) + m_d(v_f)
since all of the masses are equal i cross all of them out.
60 = 4v_f
v_f = 15m/s
 
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  • #2
chaotiiic said:

Homework Statement


Three boxcars are rolling along a virtually frictionless track at 20m/s when they strike another boxcar sitting motionless on the track. what is the new speed of the 4 coupled bovcars? all the boxcars have the same mass


Homework Equations


3rd or 2nd Newton law


The Attempt at a Solution


m_a(20) + m_b(20) + m_c(20) + m_d(0) = m_a(v_f) + m_b(v_f) + m_c(v_f) + m_d(v_f)
since all of the masses are equal i cross all of them out.
60 = 4v_f
v_f = 15m/s

That is the correct answer to the problem you described.
 
  • #3
PeterO said:
That is the correct answer to the problem you described.
thankyou.
 

1. What happens when 3 boxcars moving along a frictionless track hit a motionless boxcar?

When three boxcars moving along a frictionless track hit a motionless boxcar, the motionless boxcar will begin to move with the same velocity and direction as the three boxcars. This is due to the law of conservation of momentum, which states that the total momentum of a system remains constant unless acted upon by an external force.

2. Will the motionless boxcar experience any change in its initial velocity?

Yes, the motionless boxcar will experience a change in its initial velocity. As the three boxcars collide with the motionless boxcar, they transfer their momentum to it, causing it to move with the same velocity and direction as the three boxcars.

3. What if the track is not frictionless?

If the track is not frictionless, the motionless boxcar will experience a change in its initial velocity, but it may not have the same velocity and direction as the three boxcars. Friction will act on the boxcars, causing them to slow down and potentially change direction upon impact.

4. Is the mass of the boxcars a factor in this scenario?

Yes, the mass of the boxcars is a factor in this scenario. The momentum of an object is directly proportional to its mass, so the larger the mass of the boxcars, the greater their impact on the motionless boxcar.

5. What other factors may affect the outcome of this scenario?

The speed of the boxcars, the angle at which they collide with the motionless boxcar, and the elasticity of the boxcars and track are all factors that may affect the outcome of this scenario. A higher speed or a more oblique angle of collision may result in a greater change in the motionless boxcar's velocity. A more elastic track may also affect the transfer of momentum between the boxcars.

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