Rita throws a ball straight up into the air and catches it at the
2 answers:
(1) The potential energy at the top of the ball’s motion is 18 J.
(3) The kinetic energy increases as the potential energy decreases.
(4) The kinetic energy decreases as the potential energy increases.
(5) The total mechanical energy of the ball stays constant.
Explanation:
The total mechanical energy of the ball is equal to the sum of its kinetic energy (K, energy due to the motion) and its potential energy (U, energy due to the height of the ball). Mathematically:
In absence of friction, the mechanical energy of the ball is conserved, so in this case, it is always equal to 18 J. Let's now use this information to analyze each of the given statements:
(1) The potential energy at the top of the ball’s motion is 18 J. --> TRUE. In fact, at the top, the ball's speed becomes zero, so its kinetic energy is zero: K = 0. This means that all the mechanical energy of the ball is potential energy, therefore
E = U = 18 J
(2) The kinetic energy is less when the ball is thrown than when it is caught. --> FALSE. As we said, in absence of friction, the mechanical energy is conserved, therefore it always remains equal to 18 J.
(3) The kinetic energy increases as the potential energy decreases. --> TRUE. As we said, the sum of potential+kinetic energy remains constant:
E = K + U = 18 J
therefore, when the potential energy decreases, the kinetic energy increases.
(4)The kinetic energy decreases as the potential energy increases. --> TRUE. For the same reason described in (3).
(5)The total mechanical energy of the ball stays constant. --> TRUE. As we said at the beginning, the total mechanical energy is constant.
(6) The mechanical energy decreases as the ball moves up and increases as the ball comes down. --> FALSE. As we said, the mechanical energy remains constant, so it cannot change.
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Answer: 114
Explanation:
The mass number of an element gives the sum of the protons and the neutrons inside the nucleus of one atom of that element, while the atomic number of an element gives the number of protons inside one atom of that element.
We can infer the number of neutrons inside one atom of Osmium from its mass number and atomic number.
The atomic number of osmium is 76, so each atom of osmium has 76 protons
The (average) mass number of osmium is 190, so each atom of osmium has (on average) 190 protons+neutrons
So, in order to find the average number of neutrons, we can subtract the atomic number from the mass number:
4m/s due north of the store
Explanation:
Given parameters:
Time taken = 45s
Displacement = 180m
Unknown
Velocity = ?
Solution:
Velocity is the displacement of a body per unit time. Velocity is a vector quantity that has both magnitude and direction.
Velocity = =
Velocity = 4m/s due north of the store
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