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gulaghasi [49]
2 years ago
9

A 40kg girl and a 50kg boy are facing each other on a friction-free rollerskates. The girl pushes the boy, who moves away at a s

peed of 3 m/s. What is the girl's
speed?
Your answer
Physics
1 answer:
ki77a [65]2 years ago
5 0

Answer:

Explanation:

The Law of Momentum Conservation, just like the Law of Thermodynamics about energy, says that momentum is neither created nor destroyed but is conserved, meaning it has to go somewhere. If the girl pushes the boy and they are both on friction free skates, then the girl will also react to the push. Momentum Conservation says

(m_gv_g+m_bv_b)_b=(m_gv_g+m_bv_b)_a In words this says that the mass times the velocity of the girl plus the mass times the velocity of the boy before the push has to equal the mass times velocity of the girl plus the mass times velocity of the boy after the push. Mathematically,

(40.0*0+50.0*0)_b=(40.0v+50.0*-3)_a

The left side of this is equal to 0. On the right, I made the velocity of the boy negative. We could have made it positive and it wouldn't have mattered. The sign will only be important to the result because if the sign of the girl's velocity is the same as the boy's, she is moving in the same direction as he is; if it's different, she is moving in the opposite direction.

0 = 40.0v - 150.0 and

-40.0v = -150.0 so

v = 3.75 This means that when she pushes the boy one way, mometum is conserved and she moves in the opposite direction and at a greater velocity (because her mass is less). Physics is a wonderful thing, isn't it!?

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PLEASE HELP ME WITH THIS PROBLEM
valentinak56 [21]

1) The mass of the continent is 2.13\cdot 10^{21} kg

2) The kinetic energy of the continent is 274.8 J

3) The speed of the jogger must be 2.76 m/s

Explanation:

1)

The continent is a slab of side 5900 km (so the surface is 5900 x 5900, assuming it is a square) and depth 26 km, therefore its volume is:

V=(36)(4600)^2=7.62\cdot 10^8 km^3 = 7.62\cdot 10^{17} m^3

The mass of the continent is given by

m=\rho V

where:

\rho = 2790 kg/m^3 is its density

V=7.62\cdot 10^{17} m^3 is its volume

Substituting, we find the mass:

m=(2790)(7.62\cdot 10^{17})=2.13\cdot 10^{21} kg

2)

To find the kinetic energy, we need to convert the speed of the continent into m/s first.

The speed is

v = 1.6 cm/year

And we have:

1.6 cm = 0.016 m

1 year = (365)(24)(60)(60)=3.15\cdot 10^7 s

So, the speed is

v=\frac{0.016 m}{3.15 \cdot 10^7 s}=5.08\cdot 10^{-10}m/s

Now we can find the kinetic energy of the continent, which is given by

K=\frac{1}{2}mv^2

where

m=2.13\cdot 10^{21} kg is the mass

v=5.08\cdot 10^{-10}m/s is the speed

Substituting,

K=\frac{1}{2}(2.13\cdot 10^{21})(5.08\cdot 10^{-10})^2=274.8 J

3)

The jogger in this part has the same kinetic energy of the continent, so

K = 274.8 J

And its mass is

m = 72 kg

We can write his kinetic energy as

K=\frac{1}{2}mv^2

where

v is the speed of the man

And solving the equation for v, we find his speed:

v=\sqrt{\frac{2K}{m}}=\sqrt{\frac{2(274.8)}{72}}=2.76 m/s

Learn more about kinetic energy:

brainly.com/question/6536722

#LearnwithBrainly

3 0
2 years ago
________ capture solar energy and use photosynthesis to produce sugars.
vovikov84 [41]

Answer:

Option (A)

Explanation:

The green plants are capable of synthesizing their own food, in the presence of sunlight, CO₂ and water, and in return, liberates food and oxygen (O₂). This process is known as photosynthesis. This process is possible due to the presence of chlorophyll pigments on the plant leaves.

These green plants are also known as producers, because they are able to generate food for the consumers.

Thus, the correct answer is option (A).

8 0
3 years ago
Si un ciclista se mueve a una velocidad de 5 m/s y acelera 1 m/s2, a los 10 segundos su velocidad será
MrRa [10]

Answer:

A los 10 segundos su velocidad será 15 \frac{m}{s}

Explanation:

La aceleración de un objeto es una magnitud que indica cómo cambia la velocidad del objeto en una unidad de tiempo.

En otras palabras, la aceleración relaciona los cambios de la velocidad con el tiempo en el que se producen, es decir que mide cómo de rápidos son los cambios de velocidad:

  • Una aceleración grande significa que la velocidad cambia rápidamente.
  • Una aceleración pequeña significa que la velocidad cambia lentamente.
  • Una aceleración cero significa que la velocidad no cambia.

La aceleración "a" puede ser calculada mediante la expresión:

a=\frac{vfinal - vinicial}{tiempo}

En este caso:

  • a= 1 \frac{m}{s^{2} }
  • vfinal= ?
  • vinicial= 5 \frac{m}{s}
  • tiempo= 10 s

Reemplazando:

1\frac{m}{s^{2} }=\frac{vfinal - 5\frac{m}{s} }{10 s}

Resolviendo se obtiene:

1 \frac{m}{s^{2} } *10 s= vfinal - 5 \frac{m}{s}

10 \frac{m}{s} = vfinal - 5 \frac{m}{s}

10 \frac{m}{s} + 5 \frac{m}{s} = vfinal

15 \frac{m}{s} = vfinal

<u><em>A los 10 segundos su velocidad será 15 </em></u>\frac{m}{s}<u><em></em></u>

5 0
2 years ago
Which of the following experiments could be used to determine the inertial mass of a block? A. Place the block on a rough horizo
valentinak56 [21]

Answer:

D, using a spring scale to exert a force on the block. Measure the acceleration of the block and the applied force

Explanation:

For this you would use the net force equation acceleration=net force * mass however you will want to isolate mass so it would be acceleration/ net force to get mass. Then process of elimination comes to play.

3 0
3 years ago
The earth has a vertical electric field at the surface,pointing down, that averages 102 N/C. This field is maintained by various
Schach [20]

Answer:

q  =  -461532.5 \ C

Explanation:

From the question we are told that

     The  electric filed is  E  =  102 \ N/C  

Generally according to Gauss law

=>   E  A  =  \frac{q}{\epsilon_o }

Given that  the electric field is pointing downward  , the equation become

    - E  A  =  \frac{q}{\epsilon_o }

Here   q is the excess charge on the surface of the earth

          A is the surface  area of the of the earth which is mathematically represented as

     A  =  4\pi r^2

Where r is the radius of the earth which has a value r = 6.3781*10^6 m

 substituting values

    A  = 4 * 3.142  *   (6.3781*10^6 \ m)^2

    A  =5.1128 *10^{14} \ m^2

So

   q  =  -E  * A  *  \epsilon _o

Here \epsilon_o s the permitivity of free space with value

          \epsilon_o  =  8.85*10^{-12} \  m^{-3} \cdot kg^{-1}\cdot  s^4 \cdot A^2

substituting values

     q  =  -102  * 5.1128 *10^{14}  *  8.85 *10^{-12}

     q  =  -461532.5 \ C

6 0
3 years ago
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