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A 250 kg flatcar 25 m long is moving with a speed of 3.0 m/s along horizontal frictionless rails. A 61 kg worker starts walking from one end of the car to the other in the direction of motion, with speed 2.0 m/s with respect to the car. In the time it takes for him to reach the other end, how far has the flatcar moved?

Respuesta :

Answer:

x=31.09m

Explanation:

p1=p2

The momentum of flatcar and the momentum of the worker so

The velocity of the worker is:

[tex]m_{f}*v_{f}=m_{w}*v_{w}\\\\v_{f}=\frac{m_{f}*v_{f}}{m_{w}}\\v_{f}=\frac{61kg*3.0\frac{m}{s}}{250kg}\\v_{f}=0.732\frac{m}{s}[/tex]

The total motion has a total velocity and is

[tex]Vt=v_{w}+v_{f}\\Vt=0.732\frac{m}{s}+3.0\frac{m}{s}\\Vt=3.732\frac{m}{s}[/tex]

The time the worker take walking is

[tex]t=\frac{x}{v_{w}}\\t=\frac{25m}{3\frac{m}{s}}=8.33s[/tex]

Now the total time and the total velocity determinate the motion of tha flatcar how far has moved

[tex]x=t*Vt\\x=8.33s*3.732\frac{m}{s} \\x=31.09m[/tex]

The time it takes for him to reach the other end of the flatcar is 8.9s.

The distance traveled by the flatcar during this time is 26.7 m.

The given parameters;

  • mass of the flatcar, m = 250 kg
  • length of the flat car, L = 25 m
  • velocity of the flatcar, v = 3 m/s
  • speed of the worker, vâ‚‚ = 2 m/s

Apply the principle of conservation of linear momentum, assuming that their momentum before collision is equal to the momentum after collision.

[tex]m_1u_1 + m_2 u_2 = v(m_1+ m_2)\\\\(250\times 3) + (61 \times 2) = v(250 + 61)\\\\872 = 311v\\\\v = \frac{872}{311} \\\\v = 2.8 \ m/s[/tex]

The time it takes for him to reach the other end of the flatcar is calculated as follows;

[tex]t = \frac{25 \ m}{2.8 \ m/s} \\\\t = 8.9 \ s[/tex]

The distance traveled by the flatcar during this time is calculated as;

d = 3 x 8.9

d = 26.7 m

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