15. Define centripetal acceleration. Give its direction. Write the 3 expression for the centripetal acceleration. If the time period of
rotation of a body in a circular path is increased by three times then
what is the effect on the centripetal .

Ans 1 :Centripetal acceleration, property of the motion of a body traversing a circular path.

Ans 2 :The acceleration is directed radially toward the centre of the circle and has a magnitude equal to the square of the body's speed along the curve divided by the distance from the centre of the circle to the moving body

Ans 3 :We can express the magnitude of centripetal acceleration using either of two equations: ac=v2r;ac=rω2 a c = v 2 r ; a c = r ω 2

Ans 4 :The angular speed along a given circular path is inversely proportional to time of revolution,so if the time of revolution is increased by 3 times then the angular speed becomes 1/3 rd

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the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.