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3 years ago

A) How many joules of energy does a 100-watt light bulb use per hour? Express your answer using two significant figures.

Physics

1 answer:

kenny6666 [7]3 years ago

5 0

A) $3.6\cdot 10^5 J$

The power used by an object is defined as

$P=\frac{E}{t}$

where

E is the energy used

t is the time elapsed

In this problem, we have

P = 100 W is the power of the light bulb

t = 1 h = 3600 s is the time elapsed

Solving for E, we find the amount of energy used by the light bulb:

$E=Pt = (100 W)(3600 s)=3.6\cdot 10^5 J$

B) $1.1 \cdot 10^2 m/s$

The kinetic energy of an object is given by

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

where

m is the mass

v is the speed of the object

In this problem, we have a man of mass

m = 65 kg

we want its kinetic energy to be

$E=3.6\cdot 10^5 J$

Therefore, we can calculate its speed from the previous formula:

$v=\sqrt{\frac{2K}{m}}=\sqrt{\frac{2(3.6\cdot 10^5 J)}{65 kg}}=105.2 m/s = 1.1 \cdot 10^2 m/s$

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The Whirlpool galaxy is about 30 million light-years away. If you were in a spaceship that could travel at half of the speed of

Nataly_w [17]

Answer:

51.96 years

2) 30 million of years

Explanation:

First we must know the travel time of the ship seen from the earth. The spaceship travels at half the speed of light, this means that the amount of time the spacecraft must spend to travel the same distance is double compared to the light, that is 60 years.

Now due to the speed of the ship, we must take into account relativistic effects, such as time dilation, this is given by:

$t'=\frac{t}{\sqrt{1-\frac{v^2}{c^2}}}$

Where t is the time measured in the ship, t' is the time measured in the earth, inertially moving with velocity v.

Rewriting for t:

$t=t'\sqrt{1-\frac{v^2}{c^2}}\\t=60\sqrt{1-\frac{(0.5c)^2}{c^2}}\\t=60\sqrt{1-0.5^2}\\t=51.96 years$

This is the amount of time it would take you reach the Whirlpool galaxy in the spaceship.

2) a light year is a measure of distance, which indicates the kilometers that light travels in a year. Thus, the light emitted by Whirlpool galaxy takes 30 million of years reaches our planet.

6 0

3 years ago

Practice entering numbers that include a power of 10 by entering the diameter of a hydrogen atom in its ground state, dH = 1.06

Slav-nsk [51]

Answer:

$1.06085\times 10^{-10}\ m$

Explanation:

h = Planck's constant = $6.626\times 10^{-34}\ m^2kg/s$

m = Mass of electron = $9.11\times 10^{-31}\ kg$

k = Coulomb constant = $8.99\times 10^{9}\ Nm^2/C^2$

e = Charge of electron = $1.6\times 10^{-19}\ C$

n = 1 (ground state)

Angular momentum is given by

$L=mvr$

From Bohr's atomic model we have

$L=\dfrac{nh}{2\pi}$

$mvr=\dfrac{nh}{2\pi}\\\Rightarrow v=\dfrac{nh}{2\pi mr}$

The centripetal force will balance the electrostatic force

$\dfrac{ke^2}{r^2}=\dfrac{mv^2}{r}\\\Rightarrow \dfrac{ke^2}{r}=mv^2\\\Rightarrow \dfrac{ke^2}{r}=m(\dfrac{nh}{2\pi mr})^2\\\Rightarrow r=\dfrac{n^2h^2}{4\pi^2mke^2}\\\Rightarrow r=\dfrac{1^2\times (6.626\times 10^{-34})^2}{4\pi^2 \times 9.11\times 10^{-31}\times 8.99\times 10^{9}\times (1.6\times 10^{-19})^2}\\\Rightarrow r=5.30426\times 10^{-11}\ m$

The diameter is $2\times 5.30426\times 10^{-11}=1.06085\times 10^{-10}\ m$

7 0

3 years ago

20 points and brainiest

DIA [1.3K]

Answer:

electrical energy sometimes.

Explanation:

125.0m

300 degree Fahrenheit

7 0

2 years ago

Give an example of a force applied to an object that does not change the object's velocity. Why does the object's velocity not c

Xelga [282]

Answer:

A chair at rest on the floor has two forces acting on it its own weight that pulls it downward and the floor pushing upward on the chair, both of these forces are acting on it but the net force is 0, so the chair remains at rest and its velocity stays at 0.

8 0

1 year ago

Does the sun always shine directly overhead at the equator at noon

Nikitich [7]

The sun always shines directly overhead at noon. This is because the equator always gets the equivalent amount of sunlight. The area always get 12 hours of sunlight, because it's 0 degrees north and south and it's at the center of the Earth.

4 0

2 years ago