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Physics A2 Mechanics Circular Velocity

Communications satellites orbit above the equator in orbits of radius 4.24x107 with a period of 24 hours. Calculate the angular velocity of a communications satellite and the centripetal acceleration that it experiences.

So, 2πrT=v\frac{2\pi r}{T}=v
2π×(4.24×107)24×60×60=v\frac{2\pi \times (4.24\times10^{7})}{24 \times 60 \times 60}=v
Right?
Well, that's orbital speed. You want angular velocity.
do you know a formula that connects the two?
Reply 2
Avatar for halpme
halpme
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7
Original post by Stonebridge
Well, that's orbital speed. You want angular velocity.
do you know a formula that connects the two?


Got that one...
So, a racing car of mass 500kg goes around a cirrcular racetrack with a diameter 350m at a speed of 150km per hour. What is the centripetal force acting on the car?

I do:
F=mv2rF=\frac{mv^2}{r}
F=500×1503.6350÷2F=\frac{500\times \frac{150}{3.6}}{350 \div 2}
F=4960NF=4960N
Answer says: 2500N
Reply 3
Avatar for Qari
Qari
20
Original post by halpme
Got that one...
So, a racing car of mass 500kg goes around a cirrcular racetrack with a diameter 350m at a speed of 150km per hour. What is the centripetal force acting on the car?

I do:
F=mv2rF=\frac{mv^2}{r}
F=500×1503.6350÷2F=\frac{500\times \frac{150}{3.6}}{350 \div 2}
F=4960NF=4960N
Answer says: 2500N


What is the 3.6?

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Reply 4
Avatar for Bow Tie
Bow Tie
14
Original post by Qari
What is the 3.6?

Posted from TSR Mobile


I was wondering that, and also you measure in metres per second so convert 150kmh^-1 to ms^-1 to use in the equation.
Reply 5
Avatar for halpme
halpme
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Original post by Qari
What is the 3.6?

Posted from TSR Mobile


Original post by The_Top_Hat
I was wondering that, and also you measure in metres per second so convert 150kmh^-1 to ms^-1 to use in the equation.



3.6 converts it to m/s... 150×100060×60≡1503.6\frac{150\times 1000}{60\times 60}\equiv \frac{150}{3.6}
Reply 6
Avatar for Bow Tie
Bow Tie
14
Original post by halpme
3.6 converts it to m/s... 150×100060×60≡1503.6\frac{150\times 1000}{60\times 60}\equiv \frac{150}{3.6}


Ah ok, didn't look to figure it out. It's just most people when they have some sort of problem post their bare basic working so people can check first of all to make sure they didn't make an elementary error. I just didn't see it when I glanced at it :s-smilie:

I've done the question now properly I have looked at it and I agree with your answer. Must be a mistake in the mark scheme.
Reply 7
Avatar for Qari
Qari
20
Original post by halpme
3.6 converts it to m/s... 150×100060×60≡1503.6\frac{150\times 1000}{60\times 60}\equiv \frac{150}{3.6}


The fracs confuse me

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Reply 8
Avatar for Bow Tie
Bow Tie
14
Original post by Qari
The fracs confuse me

Posted from TSR Mobile


150kmh -> Xms

150km = 150000m

hour = 60 (minutes) x 60 (Seconds)

so 150kmh = (150000)/(60x60)ms^-1

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