How to determine the diameter of a rod using thread an meter scale?
You are given a sufficiently long piece of thread, a meter stick and a thin round shape iron rod. Explain how would you measure the diameter of iron rod by using given thread and meter stick.
Yosef asked
Answer:
Wind the thread over the rod closely a number of times say 20 and mark the end point. Now unwind it and measure the length of the thread used to wind over the rod.
This length = n x 2πr, where n is the no. of windings and r is the radius of the rod.
Therefore, the diameter of the rod = 2r = The length of wire used for ‘n’ windings /nπ
Categories: Ask Physics, How to, Interesting Questions Tags: diameter, measurement.length, Physics Fundamentals, radius, screw gauge
The Physics of Breaking Stuff – The Physics of Martial Arts
How is Physics applied in Breaking things in Karate Demonstrations?
Answer:
The following video explains it well. If you have further doubts, please post them as comments to this post.
Categories: Ask Physics, How to, Interesting Questions, Mechanics Tags: break, breaking, karate, martial arts, physics, science of karate
How wheel + Tyre diameter affects a vehicle’s speed
I have been told a larger wheel/tyre decrease acceleration because its harder to turn the wheel making the car rev slower.
But the same person tells me it will increase the top speed.
My question is if the car has a max rev of 8000rpm but only reaches 7000rpm in its highest gear would a smaller wheel/tyre not make it easier for the car to rev higher thus possible increasing the top speed by using a smaller wheel?
(Garry asked)
Answer:
As wheel radius increases, its top speed increases for a given RPM since for a given RPM the speed of the vehicle is directly proportional to its radius.
The distance traveled in one rotation = 2 π R
But now, there is another effect also here. As the radius of tyre increases, its moment of inertia increases and it would be harder for the engine to rotate it. So, the engine will not be able to turn it with the same ease as before, but however, there will be an increase in top speed other conditions remaining the same.
Refer to http://wahiduddin.net/calc/calc_speed_rpm.htm for a calculation of top speed vs tyre radius
Categories: Ask Physics, How to, Interesting Questions, Mechanics Tags: car, diameter, max, moment of inertia, person, speed, tyre, wheel
DECREASING PRESSURE BY INCREASING AREA
The pressure exerted by a given force can be decreased by increasing the area of contact.
P=F/A
The equation shows that pressure is inversely proportional to area.
FOUNDATION OF BUILDINGS
The foundation off building is made more broader than the rest of the building so that the pressure exerted by the weight on earth can be decreased.
SHOULDER STRAPS OF SCHOOL BAGS
The shoulder straps of school bags are made wider and soft so that the pressure exerted by the heavy bags on shoulders can be reduced. You can feel the paining pressure if you try to replace the broad strap with a narrow one.
FEET OF ELEPHANT AND CAMEL
MILITARY TANK
The Military tanks have a broad chain so that the pressure exerted by the heavy vehicle on ground is a minimum and it can travel even through marshy places
- Heavy Vehicles have more tyres
- When vehicles get struck in marshy places, wooden planks are used for the vehicle to come up.
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Categories: Ask Physics, Force, How to, Mechanics, question Tags: Area, ask, ask Physics, building, doubt, foundation, Heavy Vehicles, Online, physics, pressure, project, solved, solved paper, solved problems, solved questions, vehicle, weight
