Force..orbital speed..distance??

Question

physics anyone??

1. the normal hydrogen atom consists of a proton nucleus and an orbital electron. assume that the electron orbit is circular and that the constant distance between the proton and electron is 5.3 X 10^-11 m. what is the force of attraction between the two fundamental particles?

1) 1.77 X 10^-8 N

2) 3.35 X 10^-8 N

3) 6.18 X 10^-8 N

4) 8.20 X 10^-8 N

2. what is the orbital speed of the orbiting electron?

1) 1.4 X 10^6 m/sec

2) 1.90 X 10^6 m/sec

3) 2.19 X 10^6 m/sec

4) 3.11 X 10^6 m/sec

3. a parallel-plate capacitor with air dialectric has a plate area of 75 cm^2. if the capacitor is fully charged by a 300V source and can hold a charge of 7.5 X 10^-9 C, what is the distance between the plates?

1) 2.7 mm

2) 3.1 mm

3) 5.3 mm

4) 6.9 mm

my answers are 3,2,2...am i correct???

thanks!!!

Answer 1

1. Force between two charges q1 and q2 is 9 * 10^9 * q1 * q2/distance square

Charge of proton = 1.6 * 10^-19 C and

charge on electron = - 1.6 * 10^-19 C

You can calculate the rest.

2. If orbital speed is V, then force = mV^2/R

where m = mass of electron = 9 * 10^-31 kg

R = distance of electron from proton (given in the problem)

You have calculated force in question 1.

So, you can calculate for V.

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