How long would it take for a ball dropped from the top of a 484-foot building to hit the ground? round your answer to two decima
1 answer:
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1) 29.4 N
The force of gravity between two objects is given by:
where
G is the gravitational constant
M and m are the masses of the two objects
r is the separation between the centres of mass of the two objects
In this problem, we have
(mass of the Earth)
(mass of the box)
(Earth's radius, which is also the distance between the centres of mass of the two objects, since the box is located at Earth's surface)
Substituting into the equation, we find F:
2)
Let's now calculate the ratio F/m. We have:
F = 29.4 N
m = 3.0 kg
Subsituting, we find
This is called acceleration of gravity, and it is the acceleration at which every object falls near the Earth's surface. It is indicated with the symbol .
We can prove that this is the acceleration of the object: in fact, according to Newton's second law,
where a is the acceleration of the object. Re-arranging,
which is exactly equal to the quantity we have calculated above.
Answer:
-6112.26 J
Explanation:
The initial kinetic energy, is given by
} where m is the mass of a body and
is the initial velocity
The final kinetic energy, is given by
where
is the final velocity
Change in kinetic energy, is given by
Since the skater finally comes to rest, the final velocity is zero. Substituting 0 for and 12.6 m/s for
and 77 Kg for m we obtain
From work energy theorem, work done by a force is equal to the change in kinetic energy hence for this case work done equals <u>-6112.26 J</u>