Using energy considerations and assuming negligible air resistance, show that a rock thrown from a bridge 20.0 m above water wit
h an initial speed of 15.0 m/s strikes the water with a speed of 24.8 m/s independent of the direction thrown. (Hint: show that Ki + Ui = Kf + Uf)
1 answer:
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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.