Please help


1. Who was Ptolemy and Copernicus?
2. Describe their ideas about the planets and the sun

Answer:

Answer:

A

Explanation:

i think

Answer:

effects of gravity on the Moon and Earth

Explanation:       Newton found the Moon's inward acceleration in its orbit to be 0.0027 metre per second per second, the same as (1/60)2 of the acceleration of a falling object at the surface of Earth.

Since vector B was not specified, I'll assume one at random. You can later answer your own question.

Answer:

[tex]\mid\mid \vec A+\vec B \mid \mid=\sqrt{105}[/tex]

[tex]\mid\mid \vec A-\vec B \mid \mid=\sqrt{149}[/tex]

Explanation:

Given:

[tex]\vec A=3\hat i +2\hat j+3\hat k[/tex]

And (assumed):

[tex]\vec B=-5\hat i +8\hat j-4\hat k[/tex]

Find the magnitude of

[tex]\vec A+\vec B[/tex]

[tex]\vec A-\vec B[/tex]

Given a vector

[tex]\vec P=x\hat i +y\hat j+z\hat k[/tex]

The magnitude of the vector is:

[tex]\mid\mid \vec P\mid \mid=\sqrt{x^2+y^2+z^2}[/tex]

[tex]\vec A+\vec B =3\hat i +2\hat j+3\hat k-5\hat i +8\hat j-4\hat k[/tex]

[tex]\vec A+\vec B =-2\hat i +10\hat j-\hat k[/tex]

The magnitude of the sum is:

[tex]\mid\mid \vec A+\vec B \mid \mid=\sqrt{(-2)^2+10^2+(-1)^2}=\sqrt{4+100+1}[/tex]

[tex]\mathbf{\mid\mid \vec A+\vec B \mid \mid=\sqrt{105}}[/tex]

[tex]\vec A-\vec B =3\hat i +2\hat j+3\hat k-(-5\hat i +8\hat j-4\hat k)[/tex]

[tex]\vec A-\vec B =3\hat i +2\hat j+3\hat k+5\hat i -8\hat j+4\hat k[/tex]

[tex]\vec A-\vec B =8\hat i -6\hat j+7\hat k[/tex]

The magnitude of the difference is:

[tex]\mid\mid \vec A-\vec B \mid \mid=\sqrt{8^2+(-6)^2+7^2}=\sqrt{64+36+49}[/tex]

[tex]\mathbf{\mid\mid \vec A-\vec B \mid \mid=\sqrt{149}}[/tex]

Answer:

a) [tex]H_{in}=39.34 kJ[/tex]

b) Efficiency=76.77%

Explanation:

a)

In order to solve this problem, we can use the following formula:

[tex]H_{in}=H_{out}+W[/tex]

the problem provides us with all the necessary information so we can directly use the formula:

[tex]H_{in}=9.14kJ+30.2kJ[/tex]

[tex]H_{in}=39.34 kJ[/tex]

b) In order to find the efficiency, we can use the following formula:

[tex]Efficiency=\frac{W}{H_{in}}*100\%[/tex]

so we get:

[tex]Efficiency=\frac{30.2kJ}{39.34kJ}*100\%[/tex]

Efficiency=76.77%

Answer: Final temperature is 34.15°C.

Explanation: When two objects have different temperature, they will exchange heat energy until there is no more net energy transfer between them. At that state, the objects are in thermal equilibrium.

So, when in equilibrium, the total heat flow must be zero, i.e.:

[tex]Q_{1}+Q_{2}=0[/tex]

In our case, there will be a change in state of ice into water, so total heat flow will be:

[tex]m_{1}c_{1}(T_{f}-T_{i})+m_{2}c_{2}(T_{f}-T_{i})+mL=0[/tex]

where

m₁ is mass of ice

m₂ is mass of water

c₁ is specific heat of ice

c₂ is specific heat of water

[tex]T_{f}[/tex] is final temperature

[tex]T_{i}[/tex] is initial temperature

L is latent heat fusion

Temperature is in Kelvin so the transformation from Celsius to Kelvin:

For ice:

T = -15 + 273 = 258K

For water:

T = 48 + 273 = 321K

Solving:

[tex]21(2.09)(T_{f}-258)+158(4.186)(T_{f}-321)+21(333)=0[/tex]

[tex]43.89T_{f}-11323.62+661.4T_{f}-212305.55+6993=0[/tex]

[tex]705.3T_{f}=216636.17[/tex]

[tex]T_{f}=[/tex] 307.15K

In Celsius:

[tex]T_{f}=[/tex] 34.15°C

Final temperature of the system when in equilibrium is 34.15°C

Answer:

The drill's angular displacement during that time interval is 24.17 rad.

Explanation:

Given;

initial angular velocity of the electric drill, [tex]\omega _i[/tex] = 5.21 rad/s

angular acceleration of the electric drill, α = 0.311 rad/s²

time of motion of the electric drill, t = 4.13 s

The angular displacement of the electric drill at the given time interval is calculated as;

[tex]\theta = \omega _i t \ + \ \frac{1}{2}\alpha t^2\\\\\theta = (5.21 \ \times \ 4.13) \ + \ \frac{1}{2}(0.311)(4.13)^2\\\\\theta = (21.5173 ) \ + \ (2.6524)\\\\\theta =24.17 \ rad[/tex]

Therefore, the drill's angular displacement during that time interval is 24.17 rad.

Answer:

Buoyant Force = 200N

Explanation:

Given

[tex]Object = 200N[/tex]

Required

Determine the buoyant force?

Using Archimedes principle:

When an object is immersed in a fluid, the object is acted upon on by an upward force (Buoyant force) which equals the weight of the object.

In other words;

Buoyant Force = Weight of object

Hence:

Buoyant Force = 200N

The buoyant force on the object which floats with three-fourths of its volume beneath the surface of the water is 200 N.

The buoyant force is the force which is applied by the fluid in the upward direction when a object is placed over it. This buoyant force can be calculated with the following formula.

[tex]F_b=-\rho gV[/tex]

Here, (ρ) is the density of the fluid, (g) is the gravitation force and (V) is the fluid volume.

The buoyant force is equal to the weight of the liquid displace by the object which is placed on it.

It is given that the 200-N object floats with three-fourths of its volume beneath the surface of the water.

This force applied on the object balance the 200-N object and floats it. For this case, the value of buoyant force will be equal to the weight of the object.

[tex]F_b=W\\F_b=200\rm\; N[/tex]

Thus, the buoyant force on the object which floats with three-fourths of its volume beneath the surface of the water is 200 N.

Learn more about the buoyant force here;

https://brainly.com/question/3228409

Answer:

Answer:

The correct answer is B. your weight

Explanation:

Newton's third law states that every action has an equal and opposite reaction. You may not think this, but when you're standing on the floor, you are exerting a force against the floor: your weight, caused by gravity, is pulling you down. The floor is reacting by pushing back: we call this force the reaction force. -Google

Answer:

kkk

Explanation:

Answer:B

Explanation: i took the test and i got it right

Answer:

m = 80[kg]

Explanation:

The kinetic energy can be calculated by means of the following equation.

[tex]E_{k}=\frac{1}{2}*m*v^{2}[/tex]

where:

m = mass [kg]

v = velocity = 5 [m/s]

Ek = kinetic energy = 1000 [J]

Now replacing:

[tex]1000 = \frac{1}{2} *m*5^{2}\\2000 = 25*m\\m=80[kg][/tex]

The mass of a ball will be "80 kg".

According to the question,

Kinetic energy, [tex]E_k[/tex] = 1000 Joules

Velocity, V = 5 m/s

As we know the formula,

→ Kinetic energy = [tex]\frac{1}{2}[/tex] × mass × (velocity)²

→      [tex]E_k = \frac{1}{2}[/tex] × m × v²

By substituting the values,

     [tex]1000= \frac{1}{2}\times m\times (5)^2[/tex]

[tex]1000\times 2=25\times m[/tex]      

     [tex]2000=25\times m[/tex]

         [tex]m = \frac{2000}{25}[/tex]

             [tex]= 80[/tex] kg

Thus the above answer is correct.

Find out more information about kinetic energy here:

https://brainly.com/question/25959744

Answer:100 miles

Explanation:

Answer:

10 Km

Explanation:

He is going 5km per hour and he arrived at his friend's house in 2 hours. You multiply 5 by 2 and you get 10.

Answer: 0.3m/s/s

(i'm really sorry if i'm wrong)

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Answer:

The half-life is [tex] t_{1/2} = 1.005 h[/tex]

Explanation:

Using the decay equation we have:

[tex]A=A_{0}e^{-\lambda t}[/tex]

Where:

We know the activity decrease by a factor of two in a one hour period (t = 1 h), it means that [tex]A = \frac{A_{0}}{2}[/tex]

[tex]\frac{A_{0}}{2}=A_{0}e^{-\lambda*1 h}[/tex]

[tex]0.5=e^{-\lambda*1 h}[/tex]

Taking the natural logarithm on each side we have:

[tex]ln(0.5)=-\lambda[/tex]

[tex]\lambda=0.69 h^{-1}[/tex]

Now, the relationship between the decay constant λ and the half-life t(1/2) is:

[tex]\lambda = \frac{ln(2)}{t_{1/2}}[/tex]

[tex] t_{1/2} = \frac{ln(2)}{\lambda}[/tex]

[tex] t_{1/2} = \frac{ln(2)}{0.69}[/tex]

[tex] t_{1/2} = 1.005 h[/tex]

I hope it helps you!

Answer:

D i think

Explanation:

Heavier objects (objects with more mass) are more difficult to move and stop.

Answer:

Increasing the mass of the object (option D in the list of answers)

Explanation:

Recall that F = m x a

therefore, if the mass increases, the force increases

Answer:

Object's weight = 6,839.42 N

Explanation:

Given

Above waterline = 30%

Volume of object = 1m^3

Required

Determine the weight of the object

First, we need to calculate its Mass

Mass = Density of Water * Volume of object in water

Density of water = 997kg/m³

If 30% is above waterline, then 70% is in water.

So:

Mass = Density of Water * Volume of object in water

Mass = 997kg/m³ * 70%m³

Mass = 997kg * 70%

Mass = 697.9 kg

The object weight sis then calculated as thus:

Weight = Mass * Acceleration of gravity

Weight = 697.9 kg * 9.8m/s²

Weight = 6 839.42 N

Answer:

the air is being stopped in the pocket of the parachutes theys why the parachute has a certain shape so that the air that gets caught inside of it as the skydiver goes down slows down the landing

Answer:

The answer is "Option D"

Explanation:

Its ranges referring to the harmonic currents of its organ pipe which are open at one end and shut at another side could be noticed saying whether a strange amount of quarter-wavelengths should equal the length of its pipe. It's also the fourth wavelengths principle to have enough space and consume a minimum of 25% of our design frequency, as we're going to be taking 40 Hz.

Answer:

a) h(g) = 358,53 m

b) t = 8,16 s

c) t(t) = 16,71 s

Explanation:

Equations for vertical shooting are:

Vf = V₀ -  g * t   ;     h  =  V₀*t -  (1/2)*g*t²  ;    Vf² = V₀² - 2*g*h

And at maximum heigt Vf = 0 then

0 = V₀ - g * t

t = V₀/g                     V₀  = 80 m/s      and   g = 9,8 m/s²

t  =  80 / 9,8   (s)

t = 8,16 s

Then 8,16 s is the time to get maximum height

If we plug t = 8,16 (s) in equation  h  =  V₀*t -  (1/2)*g*t²

we get:     h (max)  =  (80)*8,16 - 0,5*9,8*(8,16)² (m)

h (max) = 652,8  -  326,27 m

h (max) = 326,53 m

Then relative to ground that height becomes

h(g) = 326,53 + 32

h(g) = 358,53 m

In order to get the time the arrow is in the air we proceed as follows:

a) for the arrow to be at the launched point will take the same time that from the launched point to the maximum height, and after that we have to find out the time the arrow takes from 32 m down to the ground level

Then  

t(t) = 8,16 + 8,16 + tₓ     (2)

Where tₓ  is the time from 32 m height to ground

h  =  V₀*tₓ -  (1/2)*g*tₓ²  but since the arrow now is going down then we change the sign of the second term on the right side of the equation

32 = (80)*tₓ  +  0,5 * 9,8 * tₓ²     Note that when the arrow is at 32 m height the speed is again V₀ = 80 m/s

32 = 80*tₓ  + 4,9*tₓ²

A second-degree equation for tₓ, solving it

4,9*tₓ² + 80*tₓ - 32 = 0

t₁,₂ = -80 ± √ 6400 + 627,2 / 9,8

t₁,₂ =( - 80 ± 83,8 ) / 9,8

there is not a negative time therefore we dismiss such solution and

t₁ = 3,8 / 9,8

t₁ = 0,39 s

And

t(t) = 8,16 + 8,16 + 0,39  s

t(t) = 16,71 s

Answer: Plates shifting

Explanation: After years and years of plates colliding into solid rock, they slowly become closer together. As recent studies have shown, Africa is currently moving closer to Europe one centimeter every year (one inch every 2.5 years).

Answer:

nvudbwasivnjlscv bwbfvsz

Explanation:

Answer:

in a spontaneous process, the entropy of the universe increases.

Explanation:

Entropy is a measure of of the degree of  randomness or disorderliness in a system.

The second law of thermodynamics can be stated as follows; "in any spontaneous process, the entropy of the universe increases."  

The universe here refers to the system's disorder and the disorder of the surroundings.  Therefore, a spontaneous process can occur, in which the entropy of the system decreases, only if the entropy increases in the surroundings.

For instance, when ice freezes, the entropy of liquid water decreases, that is, the entropy of the system decreases. However, heat is given off to the surroundings and the entropy of the surroundings increases. This is an obvious expression of this law.

Answer:

A) 2.650 km

Explanation:

The relationship between acceleration of gravity and gravitational constant is:

[tex]g = \frac{Gm}{R^2}[/tex] ---- (1)

Where

[tex]R = 6,400 km[/tex] -- Radius of the earth.

From the question, we understand that the gravitational field of the rocket is 50% of its original value.

This means that:

[tex]g_{rocket} = 50\% * g[/tex]

[tex]g_{rocket} = 0.50 * g[/tex]

[tex]g_{rocket} = 0.5g[/tex]

For the rocket, we have:

[tex]g_{rocket} = \frac{Gm}{r^2}[/tex]

Where r represent the distance between the rocket and the center of the earth.

Substitute 0.5g for g rocket

[tex]0.5g = \frac{Gm}{r^2}[/tex] --- (2)

Divide (1) by (2)

[tex]\frac{g}{0.5g} = \frac{Gm}{R^2}/\frac{Gm}{r^2}[/tex]

[tex]\frac{g}{0.5g} = \frac{Gm}{R^2}*\frac{r^2}{Gm}[/tex]

[tex]\frac{1}{0.5} = \frac{1}{R^2}*\frac{r^2}{1}[/tex]

[tex]2 = \frac{r^2}{R^2}[/tex]

Take square root of both sides

[tex]\sqrt 2 = \frac{r}{R}[/tex]

Make r the subject

[tex]r = R * \sqrt 2[/tex]

Substitute [tex]R = 6,400 km[/tex]

[tex]r = 6400km * \sqrt 2[/tex]

[tex]r = 6400km * 1.414[/tex]

[tex]r = 9 049.6\ km[/tex]

The distance (d) from the earth surface is calculated as thus;

[tex]d = r - R[/tex]

[tex]d = 9049.6\ km - 6400\ km[/tex]

[tex]d = 2649.6\ km[/tex]

[tex]d = 2650\ km[/tex] --- approximated

Answer:

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Explanation:

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