# Could you help and check my four easy dynamics tasks? [closed]

So I have four tasks to do and I have a guess for some of them but would greatly appreciate if you could help me be sure of it or clarify what I don't understand.

1. A car covers 2000m in 2 minutes and 20 seconds. The maximum velocity is 60kmph. In the beginning and in the end of its move, the car moves with the same acceleration. Determine the acceleration.
2. What are the angular velocities of the three clock hands?
3. What is the angular velocity of a car's wheel driving 54kmph if its diameter equals 150cm?
4. We have a liquid in a test-tube moving on a circle of diameter 10cm. To find the element we want to determine, we have to cause an acceleration of 100000g. How many rounds per minute does the circle have to make?

So here is what I think:

1. I'm assuming it started with 0kmph and eventually gained the said 60kmph - is it a good way to go? If so, then: $a=\frac{60kmph}{140s}≈\frac{16,7m/s}{140s}=0,1192\frac{m}{s^2}$
2. $\omega_m=\frac{2\pi}{3600s}≈\frac{6,28}{3600s}≈0,00174rad/s \\\ \omega_h=\frac{2\pi}{43200s}≈\frac{6,28}{43200s}≈0,0001453rad/s \\\ \omega_s=\frac{2\pi}{60s}≈\frac{6,28}{60s}≈0,1rad/s$
3. The diameter is 1,5m so the circumference is 9,42m. It moves 54kmph so it's 54000m/h which is 15m/s. 15m is 1,592 of the circumference so $\omega=\frac{1,592\cdot2\pi}{1s}≈10rad/s$.
4. How should I approach how to "cause an acceleration of 100000g? And why is acceleration here measured in grams?

Could you please check what I did and help me with what I did wrong or couldn't do? Thank you very much in advance.

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Hi George, and welcome to Physics Stack Exchange! Generally we discourage questions that just ask for someone to check your work. Once you have identified the specific concept that you're not sure about, that's the point at which it's appropriate to ask a question here. (In particular, the second question you asked about #4 is fine; if you wanted to just ask that, I'd be happy to reopen the question.) – David Zaslavsky Oct 11 '12 at 19:34

## closed as too localized by Qmechanic♦, David Zaslavsky♦Oct 11 '12 at 19:34

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