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7th of September 2015
Physics
Q:










Explain why,the motion of a body which is moving with constant speed in a circular path is said to be accelerated? The minute hand of a clock is 7 cm long.Find the displacement and the distance covered by it from 9:00 am to 9:30 am.


Saptarshi Lohia - CBSE - Class IX

Monday, September 07, 2015 at 18:53:PM

A:

Hi,

When an object moves in a circle, its motion is called circular motion.When an object moves along a circular path, its direction of motion as well as speed changes continuously.Thus, the motion is said to be accelerated motion as the speed (or velocity) keeps changing.Now, when the body moves in a circle with uniform speed, its motion is known as uniform circular motion.This may suggest that the motion is not accelerated. However, the direction of speed changes at each and every point along the circle. Thus, even though the speed is constant, its direction changes. Hence, the velocity changes and is an accelerated motion.

Displacement = 14cm as the minute hand moves from 12 to 6 (9:00a.m to 9:30a.m). 

Distance covered is half the circumference of the circel.

Now, we know that the circumference of the circle is 2Πr.

To move from 9:00a.m to 9:30a.m, the minute hand covers half of the clock (circle). 

So, the distance covered by the minute hand is 2∏r/2 = Πr cm = 7× (22/7) = 22 cm 

Therefore, distance = 22 cm and displacement = 14cm

Monday, September 07, 2015 at 19:02:PM