Question

You have 9 balls,equally big,equally heavy-except for one, which is a little heavier.How would you identify the heavier ball if you could use a pair of balance scales only twice?

Answer 1

Divide the 9 balls into 3 groups of 3. Compare the weight of two of those groups. 

The heavier group should then be obvious, it will either tip the scales, or, if the scales stay balanced, then it is the group you didn't include.

Now, choose 2 balls from this group and compare their weights, and using the same logic as before, the heavier ball will be obvious.

Answer 2

B

BRubber ball is faster than iron ball

BRubber ball is faster than iron ball(a) Inertia is the name for the tendency of an object in motion to remain in motion, or an object at rest to remain at rest, unless acted upon by a force. This concept was quantified in Newton's First Law of Motion. For example when a car is abruptly accelerated, drivers and passengers may feel as though their bodies are moving backward. In reality, inertia is making the body want to stay in place as the car moves forward.

BRubber ball is faster than iron ball(a) Inertia is the name for the tendency of an object in motion to remain in motion, or an object at rest to remain at rest, unless acted upon by a force. This concept was quantified in Newton's First Law of Motion. For example when a car is abruptly accelerated, drivers and passengers may feel as though their bodies are moving backward. In reality, inertia is making the body want to stay in place as the car moves forward.(b) Yes, both the balls will start rolling due to inertia of motion. The train stops due to brakes. But the balls continue to move in the direction of the train. But the balls will not roll with the same speed. Iron ball will move slower than the rubber ball because it is heavier in weight.