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WITCHER [35]
3 years ago
12

A boy drops a ball from an observation tower. The ball hits the ground in 5.0 s. What is the ball's velocity at the time of impa

ct?
A. 0 m/s
B. 98 m/s
C. 49 m/s
D. 123 m/s
Physics
1 answer:
Orlov [11]3 years ago
7 0
The answer is <span>C. 49 m/s

The kinetic equation is:
v2 = v1 + a * t

v1 - initial velocity
v2 - final velocity
a - gravitational acceleration
t - time

We know:
v2 = ?
v1 = 0 (in free fall
a = 9.8 m/s
t = 5

</span>v2 = v1 + a * t
v2 = 0 + 9.8 * 5
v2 = 0 + 49
v2 = 49 m/s
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Answer:

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The Henry's Law is given by the next expression:

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Have a nice day!          

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3 years ago
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A year 11 pupil with a mass of 55kg swinging back on their chair and falling off it at a speed of 0.6m/s. What is his kinetic en
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Answer:

Uk = 9.9 J

Explanation:

To calculate the kinetic energie (Uk), you can make use of this formula:

Uk = 0.5 * m * v²

given m = 55 kg and v = 0.6 m/s

Substituting in the formula gives:

Uk = 0.5 * 55 * (0.6)²

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Uk = 9.9 J

Extra:

Now let's examine the formula in relation to the SI units. <em>If you understand the following, it will give you great insight in how smart Phisics is inter twained by looking at formulas and their standard units. It will save you time in future to convert formulas, if you use the right standard units.</em>

The formula for kinetic energie is:

Uk = 0.5 * m * v²

Standard SI unit for mass m is kg.

Standard SI unit for speed v is m/s.

So v * v = v² and therefore v² must have the standard SI unit of m²/s².

From the formula, you see that the unit of Uk must be kg*m²/s² and since Uk is normally given in J, these both forms must be the same !

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Because almost always the right units are <em>given</em> in a question, or because sometimes you can look up a constant in a table with an exotic and seemingly complicated unit, but that says a lot about the formula which must have been some how involved!

<em>By this, I hope you now understand the implication of using the right standard SI units and how that can help you figure out what formula is needed.</em>

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Answer:

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