Answer:
∆PE = 749.7 J
At 0.9 m high, PE = 793.8 J
At 1.75 m high, PE = 1543.5 J
Answer:

Explanation:
Assume both children bodies are point particles. The total moment of inertia about the rotation axis of 2 points particles of mass 16 kg and 25 kg at 1.5 m arm length is

where
are the masses of 2 children
are their distance to the center of rotation

Answer:
Al's mass is 102.92 kg
Explanation:
As there are no external forces in the horizontal direction, the horizontal net force must be zero:
As the force is the derivative in time of the momentum, this means that the horizontal momentum is constant:

where the suffix i and f means initial and final respectively.
The initial momentum will be:

But, as they are at rest, initially


So, this means:

We know that the have an combined mass of 195 kg:
.
so:
.





Now, we can use the values:


where the minus sign appears as they are moving at opposite directions


and this is the Al's mass.
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