A 8.9 kg mass is attached to a light cord that passes over a massless, frictionless pulley. The other end of the cord is attached to a 2.9 kg mass. Use conservation of energy to determine the final speed of the masses after the heavier mass has fallen (starting from rest) 7.7 m .The acceleration of gravity is 9.8 m/s² . Answer in units of m/s.

Respuesta :

Answer:

The final speed of the masses is 8.75 m/s.

Explanation:

Given that,

Mass = 8.9 kg

Other mass = 2.9 kg

Distance = 7.7 m

Let mass [tex]M_{s}[/tex] start at its 0 Potential energy position.

Let mass [tex]M_{l}[/tex] start with potential energy from its position 4.6 m over final position.

We need to calculate the final speed of the masses

Using conservation of energy

[tex]K.E_{s}+P.E_{s}+K.E_{l}+P.E_{l}=K.E'_{s}+P.E'_{s}+K.E'_{l}+P.E'_{l}[/tex]

[tex]\dfrac{1}{2}m_{s}v^2+m_{s}gh+\dfrac{1}{2}m_{l}v^2+m_{l}gh=\dfrac{1}{2}m_{s}v^2+m_{s}gh+\dfrac{1}{2}m_{l}v^2+m_{l}gh[/tex]

Put the value in the equation

[tex]0+0+0+8.9\times9.8\times7.7=\dfrac{1}{2}m_{s}v^2+2.9\times 9.8\times7.7+\dfrac{1}{2}m_{l}v^2+0[/tex]

[tex]8.9\times9.8\times7.7-2.9\times9.8\times7.7=\dfrac{1}{2}v^2(8.9+2.9)[/tex]

[tex]\dfrac{1}{2}v^2\times11.8=452.76[/tex]

[tex]v^2=\dfrac{452.76\times2}{11.8}[/tex]

[tex]v=8.75\ m/s[/tex]

Hence, The final speed of the masses is 8.75 m/s.

Lanuel

The final speed of the masses after the heavier mass has fallen is 8.76 m/s.

Given the following data:

  • Mass A = 8.9 kg.
  • Mass B = 2.9 kg.
  • Initial velocity = 0 m/s (starting from rest).
  • Height = 7 meters.
  • Acceleration of gravity = 9.8 [tex]m/s^2[/tex]

To determine the final speed of the masses after the heavier mass has fallen 7.7 meters, we would apply the law of conservation of energy:

How to calculate the final speed.

In accordance with the law of conservation of energy, the potential energy possessed by the masses at the beginning is equal to the kinetic energy possessed by the masses after falling:

[tex]P.E = K.E\\\\m_Agh = m_Bgh+\frac{1}{2} m_Av^2+\frac{1}{2} m_Bv^2\\\\8.9 \times 9.8 \times 7.7=2.9 \times 9.8 \times 7.7+ \frac{1}{2}\times (8.9+2.9)v^2\\\\671.594=218.834+5.9v^2\\\\5.9v^2=671.594-218.834\\\\5.9v^2=452.76\\\\v=\sqrt{\frac{452.76}{5.9} } \\\\v=\sqrt{76.74}[/tex]

Final speed, v = 8.76 m/s.

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