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3 years ago

How much kinetic energy do you think a ball will have if it were dropped from a 2-m shelf

Physics

2 answers:

Levart [38]3 years ago

8 0

5 joules hope this helps

Gre4nikov [31]3 years ago

5 0

That depends on how much mass the ball has, and what planet it's on.

The kinetic energy it has when it hits the floor is the same as the potential energy it has when it's still on the shelf. That's . . .

Potential energy = (mass of the ball) (gravity) (height off the floor)

Gravity on Earth is 9.8 m/s² .

So if the shelf is on Earth, then the ball's kinetic energy when it hits the floor is . . .

Kinetic energy = (mass of the ball, in kg) (9.8 m/s²) (2 m)

Kinetic energy = 19.6 · (mass of the ball, in kg) Joules

Up in the first answer, SWIMMY says it would have about 5 Joules. That's the kinetic energy it would have IF the mass of the ball is 0.255 kilogram.

Is that a reasonable mass for a ball ? Well, an NFL football is 0.40-0.43 kilogram. An NBA basketball is 0.62 kilogram. Two major-league hardballs are 0.284-0.298 kilogram. And 5 golf- balls are 0.229 kilogram. So I guess 0.255 kilogram is not too unreasonable for a ball, and SWIMMY's estimate of 5 Joules of kinetic energy isn't bad ... after a fall from 2 meters.

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use the general formulas for gravitational force and centripetal force to derive the relationship between speed and orbital radi

MrRissso [65]

Answer:

$v = \sqrt{\frac{GM}{r}}$

Explanation:

The universal law of gravitation is defined as:

$F = G\frac{Mm}{r^{2}}$ (1)

Where G is the gravitational constant, M and m are the masses of the two objects and r is the distance between them.

The centripetal force can be found by means of Newton's second law:

$F = ma$ (2)

Since it is a circular motion, the acceleration can be defined as:

$a = \frac{v^{2}}{r}$ (3)

Where v is the velocity and r is the orbital radius.

Replacing equation (3) in equation (2) it is gotten:

$F = m\frac{v^{2}}{r}$ (4)

Hence,

$m\frac{v^{2}}{r} = G\frac{Mm}{r^{2}}$

Then, v can be isolated:

$mv^{2} = G\frac{Mmr}{r^{2}}$

$mv^{2} = G\frac{Mm}{r}$

$v^{2} = G\frac{Mm}{mr}$

$v^{2} = \frac{GM}{r}$

$v = \sqrt{\frac{GM}{r}}$

So the relationship between speed and orbital radius is given by the expression $v = \sqrt{\frac{GM}{r}}$

8 0

3 years ago

HELP.

Radda [10]

-- Mechanical waves DO require a medium in order to travel from place to place. (Sound can't travel without some material to travel through on the way.)

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3 years ago

PLEASE HELPPP ILL DO ANYTHINGGGGGG Write 1 paragraph or more and use all three of Newton’s laws of motion to describe what happe

Lilit [14]

Answer:

The image shows an object at rest, then a force pushes the car into the water. Newton's First Law describes that objects at rest remain at rest, and objects at motion remain at motion, unless they are bothered by a force. This law comes into play with the image because the object is first seen at rest, on the top of another object. Then it is seen falling, and is now in motion at it descends into the water. Newton's Second Law, F = MA, is seen in the image is the object accelerates into the water from the force. Newton's Third Law, which states 'for every action there is an equal but opposite reaction', is in this image as the object is falling, then makes contact with the water.

Explanation: Newton's Laws

4 0

3 years ago

d) Provided a recording medium (film) with sensitivity of 100uJ/cm2 and a power detector with 10mm of diameter, background measu

lara31 [8.8K]

We are given with:
Sensitivity: 100uJ/cm2
Diameter: 10mm
Background Optical Power: 8uW
Source Optical Power: 50uW

Required: exposure time

Solution:
Exposure time = sensitivity x area / (background power - source power)
= 100uJ/cm2 (π/4) (1 cm)² / (80 uW - 50 uW)
= 2.62 s

The exposure time is 2.62 seconds.

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Describe how an electromagnet is created? What makes it attract ferromagnetic materials?

professor190 [17]

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4 years ago