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Some of the fastest dragsters do not race for more than 300-400m for safety reasons. Consider such a dragster in this problem, starting a race at rest. After the light turns green, the dragster completes a 400 m race in a time t= 6.8 s.
If the dragster could continue with this average acceleration, what would its speed be, in miles per hour, after it has travelled a total distance of 1.6 km (~ 1 mile)?

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Answer:

Its speed would be 374.35 miles per hour

Explanation:

For the average acceleration we use 2nd eqn of motion:

s = (Vo)t + at²

Vo = 0 m/s (since, car is initially at rest)

s = 400 m

t = 6.8 s

Therefore, eqn. becomes:

400 m = (0 m/s)(6.8 s) + a (6.8 s)²

a = 400 m/(6.8 s)²

a = 8.65 m/s²

Now, for a distance of 1.6 km = 1600 m, with same acceleration, its final speed can be found out by 3rd eqn. of motion:

2as = Vf² - Vo²

2(8.65 m/s²)(1600 m) = Vf² - (0 m/s)²

Vf = √27681.66

Vf = 166.38 m/s

Vf = (166.38 m/s)(1 mile/1600 m)(3600 s/ 1 hr)

Vf = 374.35 miles per hour

The distance traveled by the dragster if the race continues till 1.6 km is 526.3234 miles/h.

Given to us

The distance traveled by the dragster, s = 400 m

Time taken by the dragster to complete the race, t = 6.8 s

What is the acceleration of the dragster?

The acceleration of the dragster can be found using the second equation of motion,

[tex]s=ut+\dfrac{1}{2}at^2[/tex]

When the race starts the initial velocity of the dragster was 0, as the dragster was at rest, therefore, u =0

substitute the value,

[tex]400=(0\times 6.8)+\dfrac{1}{2}\times a\times (6.8)^2[/tex]

[tex]a= \dfrac{400\times 2}{6.8^2}[/tex]

a = 17.3 m/s²

Thus, the acceleration of the dragster is 17.3 m/s².

What would be the velocity of the dragster if he traveled 1.6 km?

We can find out the final velocity of the dragster using the third equation of motion,

[tex]v^2-u^2 = 2as[/tex]

Substitute the values,

[tex]v^2-(0)^2 = 2(17.3)(1600)[/tex]

v = 235.287 m/s

Converting it to miles per hour

[tex]v = 235.287 \times \dfrac{\dfrac{1}{1609.34}}{\dfrac{1}{3600}} = 526.3234\rm\ miles/h[/tex]

Hence, the distance traveled by the dragster if the race continues till 1.6 km is 526.3234 miles/h.

Learn more about the Equation of motion:

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