A concrete column has a diameter of 380 mm and a length of 2.6 m . if the density (mass/volume) of concrete is 2.45 mg/m3, deter
1 answer:
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Answer:
they meet from the girl's original position at: 2.37 (meters)
Explanation:
We need to use the Newton's law, exactly the second law that relate force, mass and acceleration as: with this we can get both accelerations; solving for acceleration
. Now
and
. Then knowing that they both travel at the same time and assuming that the distance among the girl and the sled is: 15.0-x, so,
and
, solving for the time we get:
and
with this equations we solving for the x that is the distance between the girl and the sled after the apply the force and we get:
. Finally we get:
and replacing the values we have got:
so
so x=2.37 (meters).
Answer:
A. when the mass has a speed of zero
Explanation:
In mass-spring system, the velocity and the acceleration are in anti-phase, which means that when one of the two quantities is maximum, the other one is zero, and vice-versa.
In fact:
- When the displacement of the spring is zero (x=0), the velocity is maximum, due to conservation of energy. In fact, as the displacement is zero, the elastic potential energy of the system (given by ) is zero, therefore the kinetic energy (given by
) must be maximum, and so the velocity (v) is also maximum. On the cotnrary, acceleration (a) is directly proportional to the restoring force of the spring, given by
so we see that when x=0, then the force is zero: F=0, and so the acceleration is zero as well.
- When the displacement of the spring is maximum, the velocity is zero, due to conservation of energy. In fact, as the displacement is maximum, the elastic potential energy of the system (given by ) is maximum, therefore the kinetic energy (given by
) must be zero, and so the velocity (v) is also zero. On the cotnrary, since acceleration (a) is directly proportional to the restoring force of the spring, given by
so we see that when x=maximum, then the force is maximum, and so the acceleration is maximum as well.
Based on this, the correct answer is
A. when the mass has a speed of zero