more questions (1 Viewer)

[Danger]

1. A model aircraft of mass 400g moves at 15m/s on the end of a wire of length 25m. Calculate the tension in the wire.

2. A car of mass 1000kg attempts to take a 50m radius curve at 10m/s.

a) What is the necessary friction force by the road on the tyres to deliver the required centripetal force?

using F = mv^2/r, I got 2000N.

b) On a particular road, the maximum friction available is only half the weight force of the car. Will the car skid?

 

[wogblogger]

2. A car of mass 1000kg attempts to take a 50m radius curve at 10m/s.

a) What is the necessary friction force by the road on the tyres to deliver the required centripetal force?

using F = mv^2/r, I got 2000N.

yepp simple substitution (i hope its right lol)

b) On a particular road, the maximum friction available is only half the weight force of the car. Will the car skid?

nup car wont skid, find weight force=mg=(1000)(9.8)=9800 half this =4900N

from part b) we can see the required force on the tyres is 2000N
therefore it wont skid

alt. instead of halfing 9800 you can just start of by sub in 500kg

(som1 snd me a message if i stuffed anythin up there)

 

[Danger]

that looks right, if frictional force is less than required = skid, if > frictional force, no skid. lol I was brain dead

 

[wogblogger]

ahaha yeaa im brain dead for the >part of the day
btw where are u studyn from? as in bookz
im use'n surf'n,jacaranda (i have dot point and maq guide but i dnt use them)

 

[Danger]

im just doing questions from sheets my teacher gave out.

heres another one:

state the simple relationship between satelltile altitude, orbital speed and period.

i cant figure out which formula they are referring to.

 

[independantz]

For 1) i think you just use F=mv^2/r as tension is a force.

state the simple relationship between satelltile altitude, orbital speed and period.

i cant figure out which formula they are referring to.

T=2nr/V^2

n stands for pi.

 

[Mark576]

Independantz, there exists no formula of which you quoted. The correct formula is simply the formula for orbital speed: v = (2*pi*r)/T which is derived from the formula for speed: s = d/t and it follows simply, where d = the circumference of the orbit (2*pi*r) and t is the time taken to complete the orbit (T). :wave:

 

[Danger]

for question 1 i used f=mv^2/r but what is the r? I think the question meant 25m as the diameter of the end of a wire, therefore radius is 12.5m?

 

[wogblogger]

MARK576 haha thankz
i was lik ohh noo i dun kno this
i was lookn in al tha textbooks LOL

 

[independantz]

Independantz, there exists no formula of which you quoted. The correct formula is simply the formula for orbital speed: v = (2*pi*r)/T which is derived from the formula for speed: s = d/t and it follows simply, where d = the circumference of the orbit (2*pi*r) and t is the time taken to complete the orbit (T). :wave:

Ahh okay, thanks for that.

 

[Danger]

heres another easy one:

THe moon is a satellite of the Earth. Use its period (24 hours) and the mass (5.98 x 10^24) of the earth to calculate the distance from earth centre to la lune.

 

[Mark576]

Use: GM/(4*pi^2) = r^3/T^2, where G = 6.67 * 10^-11 N m^2 kg^-2 and T (period) is measured in seconds.

 

[Danger]

by distance from the earth to moon, im assuming they are looking for the radius? am i right? So using keplers law I found the radius to be 8.2 x 10^7m, now would I need to add the radius of the moon + earth to my answer to work out the distance?

 

[wogblogger]

umm i think keplers law is already saying that its the distance from the center of the two bodies

 

[Danger]

thanks for pointing that out