Question

A particle is kept fixed on a turntable rotating uniformly as seen from the ground

Answer 1

The acceleration given here is centripetal acceleration, because table rotates uniformly and hence tangential acceleration is zero.

Now, w is constant .

The centripetal acceleration is Rw^2.

Then. centripetal acceleration is proportional toR.

So, reducing R to R/2, the centripetal acceleration is 20/2=10 m/s^2.

Answer 2

your answer

as seen from ground the observer would find a force named centripetal force which acts in direction inside a circle and since the speed is uniform so it's a uniform circular motion

hope helps