QUOTE (stillarook @ Jan 8 2006, 03:09 AM)
please, i'm a middle schooler, not some math geek in a university
You don't need to be in university to answer those questions Question
An article states that the Earth will always make a complete revolution every twenty four hours.
Please prove that in order for this to be correct, the Earth must rotate at 1/4 degrees per minute.My Solution
24 hours = 1440 minutes
Full rotation = 360 degrees
360/1440 = 0.25 degrees per minuteQuestion
If a car brakes suddenly, there is a possibility that the vehicle will skid. Accident investigators use a formula in order to determine the velocity of the vehicle; v^2=Mu * D
Where D is the distance in metres of the skids that were made, and mu is the coefficient of friction between the tyres and the surface. (This value is variable, and entirely dependant on the surface of the road and the tyres used.)
In a 30mph speed zone, an accident occurs, and so causes skids of 28 metres in length. The investigators perform an experiment and find out that a car travelling at 10 metres per second, leaves skid marks of length 17.5 metres.
Use this data to find the value of mu. (Assume that the tyres used in the experiment were identical to those of the car in the accident.)
Also, find the velocity of the car (In mph) when the brakes were applied.
Assume that 1 mph = 0.447 metres per second.My Solution
v^2 = muD (mu is coefficient of friction)
10^2 = 17.5mu
100/17.5 = mu
therefore mu = 5.714 to 3 d.p.
Accident that takes place:
v^2 = 5.714*28
v^2 = 160 (using unshortened value of mu)
therefore v = 12.65 m/s to 2 d.p. which is 28.3 mph to 1 d.p.
Haven't checked it through, think it's ok though, might be some typos