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swat32
1 year ago
6

A brick of mass 5 kg is released from rest at a height of 3 m. How fast is it going when it hits the ground? Acceleration due to

gravity is g = 9.8 m/s2.
Physics
1 answer:
sineoko [7]1 year ago
6 0

Taking into account the definition of kinetic, potencial and mechanical energy, when the brick hits the ground, it has a speed of 7,668 m/s.

<h3>Kinetic energy</h3>

Kinetic energy is a form of energy. It is defined as the energy associated with bodies that are in motion and this energy depends on the mass and speed of the body.

Kinetic energy is defined as the amount of work necessary to accelerate a body of a given mass and at rest, until it reaches a given speed. Once this point is reached, the amount of accumulated kinetic energy will remain the same unless there is a change in speed or the body returns to its state of rest by applying a force.

The kinetic energy is represented by the following expression:

Ec= ½ mv²

Where:

  • Ec is the kinetic energy, which is measured in Joules (J).
  • m is the mass measured in kilograms (kg).
  • v is the speed measured in meters over seconds (m/s).

<h3>Potential energy</h3>

On the other hand, potential energy is the energy that measures the ability of a system to perform work based on its position. In other words, this is the energy that a body has at a certain height above the ground.

Gravitational potential energy is the energy associated with the gravitational force. This will depend on the relative height of an object to some reference point, the mass, and the force of gravity.

So for an object with mass m, at height h, the expression applied to the gravitational energy of the object is:

Ep= m×g×h

Where:

  • Ep is the potential energy in joules (J).
  • m is the mass in kilograms (kg).
  • h is the height in meters (m).
  • g is the acceleration of fall in m/s².
<h3>Mechanical energy</h3>

Finally, mechanical energy is that which a body or a system obtains as a result of the speed of its movement or its specific position, and which is capable of producing mechanical work. Then:

Potential energy + kinetic energy = total mechanical energy

<h3>Principle of conservation of mechanical energy </h3>

The principle of conservation of mechanical energy indicates that the mechanical energy of a body remains constant when all the forces acting on it are conservative (a force is conservative when the work it does on a body depends only on the initial and final points and not the path taken to get from one to the other.)

Therefore, if the potential energy decreases, the kinetic energy will increase. In the same way, if the kinetics decreases, the potential energy will increase.

<h3>This case</h3>

A brick of mass 5 kg is released from rest at a height of 3 m. Then, at this height, the brick of mass has no speed, so the kinetic energy has a value of zero because it depends on the speed or moving bodies. But the potential energy is calculated as:

Ep= 5 kg× 9.8 \frac{m}{s^{2} }× 3 m

Solving:

<u><em>Ep= 147 J</em></u>

So, the mechanical energy is calculated as:

Potential energy + kinetic energy = total mechanical energy

147 J +  0 J= total mechanical energy

147 J= total mechanical energy

The principle of conservation of mechanical energy  can be applied in this case. Then, when the brick hits the ground, the mechanical energy is 147 J. In this case, considering that the height is 0 m, the potential energy is zero because this energy depends on the relative height of the object. But the object has speed, so it will have kinetic energy. Then:

Potential energy + kinetic energy = total mechanical energy

0 J +  kinetic energy= 147 J

kinetic energy= 147 J

Considering the definition of kinetic energy:

½  5 kg×v²= 147 J

v=\sqrt{\frac{2x147 J}{5 kg} }

v=7.668 m/s

Finally, when the brick hits the ground, it has a speed of 7,668 m/s.

Learn more about mechanical energy:

brainly.com/question/17809741

brainly.com/question/14567080

brainly.com/question/12784057

brainly.com/question/10188030

brainly.com/question/11962904

#SPJ1

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Master of physics needed
Delicious77 [7]
Hey JayDilla, I get 1/3.  Here's how:
Kinetic energy due to linear motion is:
E_{linear}= \frac{1}{2}mv^2
where
v=r \omega
giving
E_{linear}= \frac{1}{2}mr^2 \omega ^2

The rotational part requires the moment of inertia of a solid cylinder
I_{cyl} =  \frac{1}{2}mr^2
Then the rotational kinetic energy is
E_{rot}= \frac{1}{2}I \omega ^2= \frac{1}{4}mr^2 \omega ^2
Adding the two types of energy and factoring out common terms gives
\frac{1}{2}mr^2 \omega ^2(1+ \frac{1}{2})
Here the "1" in the parenthesis is due to linear motion and the "1/2" is due to the rotational part.  Since this gives a total of 3/2 altogether, and the rotational part is due to a third of this (1/2), I say it's 1/3.

8 0
3 years ago
A college student holds a pail full of water by the handle and whirls it around in a vertical circle at a constant speed. The ra
Pavlova-9 [17]

The minimum speed of the water must be 3.4 m/s

Explanation:

There are two forces acting on the water in the pail when it is at the top of its circular motion:

  • The force of gravity, mg, acting downward (where m is the mass of the water and g the acceleration of gravity)
  • The normal reaction, N also acting downward

Since the water is in circular motion, the net force must be equal to the centripetal force, so:

N+mg=m\frac{v^2}{r}

Where:

g=9.8 m/s^2

v is the speed of the pail

r = 1.2 m is the radius of the circle

The water starts to spill out when the normal reaction of the pail becomes zero:

N = 0

When this occurs, the equation becomes:

mg=m\frac{v^2}{r}\\v=\sqrt{gr}

And substitutin the values of g and r, we find the minimum speed that the water must have in order not to spill out:

v=\sqrt{(9.8)(1.2)}=3.4 m/s

Learn more about circular motion:

brainly.com/question/2562955

brainly.com/question/6372960

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6 0
3 years ago
Aluminum oxide can be produced during rocket launches. Show that the sum of positive and negative charges in a unit of Al2O3 equ
Triss [41]

Answer:

The sum of positive and negative charges in a unit of Al2O3 equals zero.

Aluminium has a charge of +3 while Oxygen has a charge of -2 on each ion.

Al203 has 2 Al atoms and 3 O atoms.

Charge on Al2O3 = 2(charge on Al ion) + 3(charge on O ion)

= 2(3) + 3(-2)

= 6 - 6

= 0

Explanation:

Aluminium has 3 electrons in the outermost shell and has the tendency to lose those 3 electrons to form a positive ion and have a complete outermost shell.

Whereas, Oxygen has 6 electrons in the outermost and has the tendency to accept two more electrons to form a negative ion and have a complete outermost shell.

4 0
3 years ago
An office heater puts out 2050 btus of energy in the form of heat per hour. given that 1 btus =1.055 kj, how many megajoules of
ivolga24 [154]
<span>Assuming continuous operation (24/7), we can say that

Energy produced : Energy per hour * 24 (number of hours in a day) - 365 (number of days in a year.

Energy per hour: 2050 * 1.055 = 2162.75 kg.

So, we proceed to calculate the results

E: 2162.75 * 24 * 365 = 18,945,690 kj per year.

Now, we transform kj to megajoule, remembering that kilo is 10*3 and mega is 1'*6, so we divide the result by 1,000 in order to get the results in megajoules, and the answer would be:

18,945.69 megajoules can be produced per year.</span>
4 0
3 years ago
How many years would it take to reach the planet saturn travelling at 21 thousand miles per hour? enter your answer with 2 decim
Dmitry_Shevchenko [17]

It would take about 4.8 years to travel from earth to Saturn.

<h3>How long would it take?</h3>

We know that speed is expressed as the ratio of distance to time. In this case, we are trying to know ow many years would it take to reach the planet Saturn travelling at 21 thousand miles per hour.

Given that;

Speed = 21 thousand miles per hour

time taken = ???

Distance = 887 million miles

Speed = distance/time

speed * time = distance

time = distance/speed

time = 8.87 * 10^8 miles/2.1 * 10^4  miles per hour

time = 4.22 * 10^4 hours

If 8.766 * 10^3 hours make 1 year

4.22 * 10^4 hours  make 4.22 * 10^4 hours * 1 year/8.766 * 10^3

= 4.8 years

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8 0
1 year ago
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