Answer:
10 cm/s
Step-by-step explanation:
Given that,
Initial speed of a marble, u = 0
It starts from rest over a distance of 12-centimeters in 1.2-seconds.
We need to find its speed at the bottom of the incline. Let it is v. Speed of an object is equal to distance covered divided by time taken. So,

So, the speed of the marble at the bottom of the incline is 10 cm/s.