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3 years ago

PLEASE HELP! 3 Questions, 10 points a question, will give brainliest.

Physics

1 answer:

Basile [38]3 years ago

8 0

1) Mechanical energy is conserved in all the 4 situations

2) True

3) The potential energy of the block is 490 J

Explanation:

Mechanical energy is the sum of potential energy (PE) and kinetic energy (KE) of a body:

$E=PE+KE$

According to the law of conservation of energy, in absence of non-conservative forces (such as air resistance, friction...), the mechanical energy of a body is always conserved.

This means that the mechanical energy is conserved in all the situations described. More specifically:

- Child on a swing : there is a continuous conversion between kinetic energy and gravitational potential energy

- Pendulum : there is a continuous conversion between kinetic energy and gravitational potential energy

Bow and Arrow : there is a conversion of energy from elastic potential (when the bow is stretched) to kinetic energy (when the arrow is shot)

Roller Coaster: there is a continuous conversion between kinetic energy and gravitational potential energy

As we said, the mechanical energy of the object falling down at any point of the fall is

$E=KE+PE$

where KE is the kinetic energy and PE is the potential energy. The value of E is constant, since the mechanical energy is conserved.

The potential energy is given by

$PE=mgh$

where m is the mass of the object, g is the acceleration of gravity, h is the height of the object above the ground.

As the object falls, its height $h$ decreases, and therefore, the potential energy PE also decreases. But we said that E must remain constant: therefore, if PE decreases, this means that KE increases, therefore as the object falls, the potential energy is converted into kinetic energy (in fact, the speed of the object increases). So the statement is true.

The potential energy of an object is given by the equation

$PE=mgh$

where

m is the mass of the object

$g=9.8 m/s^2$ is the acceleration of gravity

h is the height of the object relative to the ground

For the block in this problem, we have:

m = 10 kg

h = 5 m

Substituting, we find its potential energy:

$PE=(10)(9.8)(5)=490 J$

Learn more about potential energy and kinetic energy:

brainly.com/question/6536722

brainly.com/question/1198647

brainly.com/question/10770261

#LearnwithBrainly

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In a simple RC circuit, at t=0 the switch is closed with the capacitor uncharged. If C=30µF, =50V and R=10k, what is the poten

sergij07 [2.7K]

Answer:

Voltage across the capacitor is 30 V and rate of energy across the capacitor is 0.06 W

Explanation:

As we know that the current in the circuit at given instant of time is

i = 2.0 mA

R = 10 k ohm

now we know by ohm's law

$V = iR$

$V = (2 mA)(10 kohm)$

$V = 20 volts$

so voltage across the capacitor + voltage across resistor = V

$V_c + 20 = 50$

$V_c = 30 V$

Now we know that

$U = \frac{q^2}{2C}$

here rate of change in energy of the capacitor is given as

$\frac{dU}{dt} = \frac{q}{C} \frac{dq}{dt}$

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$\frac{dU}{dt} = 0.06 W$

3 0

3 years ago

One horse is pulling a 755 kg sled straight ahead applying a force of 1988 N. If the acceleration of the sled is 1.36 m/s2, what

Inessa [10]

Answer:

The coefficient of kinetic friction is 0.13

Explanation:

Newton's second law states that the acceleration of an object is proportional to the net force on it, the factor of proportionality is the mass. So, we can express that law mathematically as:

$\sum\overrightarrow{F}=m\overrightarrow{a}$ (1)

With F the net force, m the mass and a the acceleration of the object. In our case we're interested on what's happening to the sled, then we have to analyze the forces on it, those forces are the weight and the normal force on the vertical direction and the pulling force and frictional force in the horizontal direction. So, because (1) is a vector equation we can express that in their vertical (y) and horizontal (x) components:

$F_y=ma_y$ (2)

$F_x=ma_x$ (3)

On y we have that the acceleration is zero because the sled is not moving upward or downward, remember that the net force on y is the weight (W) pointing downward and the normal force pointing upward:

$F_y=W+n=0$

Following the convention that positive is upward and negative downward, W=mg=(755)(-9.81):

$F_y=(755)(-9.81)+n=0$

$n=7406.55 N$ (4)

Now on the x direction we have the sum of the forces is the pulling force (T) and friction force (f)

$F_x=F+f=ma_x$

Choosing the direction where the horse is pulling F=1988N and the acceleration should be positive too, then:

$1988+f=m(1.36)$

$f=(755)(1.36)-1988=-961.2 N$

The negative sign means it's in the opposite direction the horse is pulling

The frictional force is related with the coefficient of kinetic friction in the next way:

$|f|=\mu_k n$

with μk the coefficient of kinetic friction, and n the normal force that we already found on (4), so we simply solve the last equation for μk:

$\mu_k=\frac{|f|}{n}=\frac{961.2}{7406.55}=0.13$

4 0

3 years ago

The speed of sound in air is 345 m/s. A tuning fork vibrates above the open end of a sound resonance tube. If sound waves have w

Delvig [45]

To develop this problem it is necessary to apply the concept of Frequency based on speed and wavelength.

According to the definition the frequency can be expressed as

$f = \frac{v}{\lambda}$

Where,

v = Velocity

$\lambda =$ Wavelength

Our value are given by,

v = 345m/s

$\lambda = 63cm$

Replacing

$f = \frac{345}{0.63}$

$f = 547.61Hz$

Therefore the frequency of the tuning fork is 547.61Hz

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3 years ago

Forces can act on an object in the same direction or in opposite. how does each situation affect the motion of the object?

Anon25 [30]

Hi pupil here's your answer ::

➡➡➡➡➡➡➡➡➡➡➡➡➡

Action and Reaction do not act on the same body !! If they acted on the same body, the resultant force will be zero and their could be never accelerated motion.

If both the forces acted on the same body, then if they are equal to opposite direction the object will remain stationary. If on of the forces is greater than other the object will move in the direction of greater force.

If both acted in the same direction there would be an accelrated motion.

⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅⬅

Hope this helps . . . . .

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3 years ago

In a series circuit what effect will adding more resistors to the circuit have

zhuklara [117]

Answer:In a series circuit, adding more resistors increases total resistance and thus lowers current. But the opposite is true in a parallel circuit because adding more resistors in parallel creates more choices and lowers total resistance. If the same battery is connected to the resistors, current will increase.

Explanation:

8 0

3 years ago