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Anastaziya [24]
3 years ago
12

How much work in joules must be done to stop a 920-kg car traveling at 90 km/h?

Physics
1 answer:
tankabanditka [31]3 years ago
3 0

Answer:

Work done, W = −287500 Joules

Explanation:

It is given that,

Mass of the car, m = 920 kg

The car is travelling at a speed of, u = 90 km/h = 25 m/s

We need to find the amount of work must be done to stop this car. The final velocity of the car, v = 0

Work done is also defined as the change in kinetic energy of an object i.e.

W=\Delta K

W=\dfrac{1}{2}m(v^2-u^2)

W=\dfrac{1}{2}\times 920\ kg(0-(25\ m/s)^2)

W = −287500 Joules

Negative sign shows the work done is done is opposite direction.

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Three boxes in contact rest side-by-side on a smooth, horizontal floor. Their masses are 5.0-kg, 3.0-kg, and 2.0-kg, with the 3.
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Answer:

(a)Look at the attached graphic

(b)

(b)-1 Equation 1  : m1= 5kg

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(b)-2 Equation 2 : m2= 3kg

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(b)-3 Equation 3 : m3= 2kg

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We apply Newton's second law:

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(a) Draw the free-body diagrams for each of the boxes

Look at the attached graphic

(b) Write Newton’s equation for each mass along the horizontal direction.

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<em>Look</em> <em>m1 free-body diagram:</em>

∑Fx = m1*a

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<em>Look</em> <em>m2 free-body diagram:</em>

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F1-F2= 3 *a Equation 2

<em>Look</em> <em>m3 free-body diagram:</em>

∑Fx = m3*a

F2 = 2*a     Equation 3

(c) What magnitude force does the 3.0-kg box exert on the 5.0- kg box?

<em>Look</em> <em>Free body diagram of the mass set</em>

∑Fx = m*a   m= m1+m2+m3= 5+3+2 = 10 kg

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<em> (d) </em><em>What magnitude force does the 3.0-kg box exert on the 2.0kg box?</em>

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