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A particle decelerates uniformly from a speed of 30 cm/s to rest in a time interval of 5.0 s. It then has a uniform acceleration of 10 cm/s2 for another 5.0 s. The particle moves in the same direction along a straight line. The average speed over the whole time interval is?

Respuesta :

Answer:

V=20cm/s

Explanation:

The average speed is the distance total divided the time total:

[tex]V=X/T[/tex]

First stage:

T1=5s

[tex]v_{f}  =v_{o} - at[/tex]

But, [tex]v_{f}  =0[/tex]   (decelerates to rest)

then: [tex]a =v_{o} /t=0.3/5=0.06m/s^{2}[/tex]

on the other hand:

[tex]x =v_{o}*t - 1/2*at^{2}=0.3*5-1/2*0.06*5^{2}=0.75m[/tex]

X1=75cm

Second stage:

T2=5s

[tex]x =v_{o}*t + 1/2*at^{2}=0+1/2*0.1*5^{2}=1.25m[/tex]

X2=125cm

Finally:

X=X1+X2=200cm

T=T1+T2=10s

V=X/T=20cm/s

Lanuel

The average speed of the particle over the whole time interval is 20 cm/s.

Given the following data:

  • Final speed A = 0 m/s (since it decelerates from rest).
  • Initial speed A = 30 cm/s
  • Time A = 5 seconds.
  • Acceleration B = 10 [tex]cm/s^2[/tex]
  • Time B = 5 seconds.

To determine the average speed over the whole time interval:

First of all, we would determine the acceleration of the particle in scenario A.

[tex]V = U - at\\\\0 = 30 - a(5)\\\\0=30-5a\\\\5a = 30\\\\a =\frac{30}{5} \\\\a =6\;cm/s^2[/tex]

Next, we would find the distance covered by the particle in scenario A.

[tex]S = ut - \frac{1}{2} at^2\\\\S = 30(5) - \frac{1}{2} \times 6 \times 5^2\\\\S = 150-3\times 25\\\\S=150-75[/tex]

Distance, S = 75 cm.

For scenario B, we would find the distance covered by the particle:

[tex]X = ut + \frac{1}{2} at^2\\\\X = 0(5) + \frac{1}{2} \times 10 \times 5^2\\\\X = 5 \times 25[/tex]

X = 125 cm.

Now, we can determine the average speed over the whole time interval:

[tex]Total \;distance = distance \;A +distance\;B\\\\Total \;distance = 75 +125[/tex]

Total distance = 200 cm

[tex]Total \;time = time \;A +time\;B\\\\Total \;distance = 5 +5[/tex]

Total time = 10 seconds.

Mathematically, average speed is given by the formula:

[tex]Average\;speed = \frac{Total\;distance}{Total\;time} \\\\Average\;speed = \frac{200}{10}[/tex]

Average speed = 20 cm/s.

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