Physics, 29.07.2019 22:00 Nathaliasmiles

A0.30-kg stone is held 1.2 m above the top edge of a water well and then dropped into it. the well has a depth of 5.1 m. (a) relative to the configuration with the stone at the top edge of the well, what is the gravitational potential energy of the stoneâearth system before the stone is released? j (b) relative to the configuration with the stone at the top edge of the well, what is the gravitational potential energy of the stoneâearth system when it reaches the bottom of the well? j (c) what is the change in gravitational potential energy of the system from release to reaching the bottom of the well? j

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(a) The gravitational potential energy of the stone before it is released is:
$U=mg \Delta h$
where m=0.30 kg is the mass of the stone, g=9.81 m/s^2

and $\Delta h$ is the difference in height relative to the reference level, which is the top edge of the well. Therefore, since the stone in this situation is at h=1.2 m above the top edge of the well, $\Delta h=1.2 m$ , and the gravitational potential energy is
U=(0.30 kg)(9.81 m/s^2)(1.2 m)=3.5 J

(b) Similarly, the gravitational potential energy when the stone reaches the bottom of the well is
$U=mg \Delta h$
but this time the stone is at the bottom of the well, so at 5.1 m below the top edge of the well, therefore $\Delta h=-5.1 m$ . So, the gravitational potential energy in this situation is
U=(0.30 kg)(9.81 m/s^2)(-5.1 m)=-15.0 J

(c) The change in gravitational potential energy from release to the bottom of the well is:
$\Delta U= U_b-U_a=-15.0 J-(3.5 J)=-18.5 J$

Answer from: Quest

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

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A0.30-kg stone is held 1.2 m above the top edge of a water well and then dropped into it. the well h...

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