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3 years ago

9

A 600kg car is at rest , and then accelerates to 5n/s what is the original kinetic energy?

1 answer:

lubasha [3.4K]3 years ago

7 0

M = 600 kg
u = 0 (as the car was at rest initially)
v = 5 m/s
Initial kinetic energy = ½mu²
= ½×600×0
= 0
Final kinetic energy = ½mv²
= ½×600×25
= 7500 J

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Two kids are playing on a newly installed slide, which is 3 m long. John, whose mass is 30 kg, slides down into William (20 kg),

yuradex [85]

Answer:

$v=3.564\ m.s^{-1}$

$\Delta v =2.16\ m.s^{-1}$

Explanation:

Given:

mass of John, $m_J=30\ kg$

mass of William, $m_W=30\ kg$

length of slide, $l=3\ m$

(A)

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u_J = initial velocity of John at the top of the slide = 0

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frictional force due to mud, $f=105\ N$

<u>Now we find the force along the slide due to the body weight:</u>

$F=m_J.g.sin\theta$

$F=30\times 9.8\times \frac{1.8}{3}$

$F=176.4\ N$

<em><u>Hence the net force along the slide:</u></em>

$F_R=71.4\ N$

<em>Now the acceleration of John:</em>

$a_j=\frac{F_R}{m_J}$

$a_j=\frac{71.4}{30}$

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<u>Now the new velocity:</u>

$v_J_n^2=u_J^2+2.(a_j).l$

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$v_J_n=3.78\ m.s^{-1}$

Hence the new velocity is slower by

$\Delta v =(v_J-v_J_n)$

$\Delta v =5.94-3.78= 2.16\ m.s^{-1}$

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