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3 years ago

Charles Darwin,

Physics

2 answers:

Roman55 [17]3 years ago

8 0

The answer is B. Artificial Selection :)

grandymaker [24]3 years ago

3 0

The answer is B artificial selection

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A person uses 750 kcal on a long walk calculate the energy used for the walk in kilojoules

guapka [62]

Basically, this problem asks you to convert kilocalories (kcal) to kilojoules (kJ). Both are units of energy. To convert kcal to kJ, the equivalence is: 1 kcal = 4.184 kJ. Through dimensional analysis, the solution is as follows:

750 kcal * 4.184 kJ/1 kcal = 3,138 kJ

6 0

3 years ago

Four discs are spinning at constant angular velocity. Four ideantical balls are dropped on the discs at different distances from

Arlecino [84]

Answer: They will have equal final angular velocity.

Explanation:

Since the discs starts from rest and rotates about a ﬁxed axis, they are subject to a constant net torque. The work done by the torque during the second revolution is as the work done during the ﬁrst revolution.

The four disc will turn through equal angles in equal times.

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2 years ago

Which of the following involves an endothermic reaction?

earnstyle [38]

Answer:

C. Plants converting sunlight into chemical energy.

Explanation:

An "endothermic reaction" is a process whereby energy coming from the surroundings is being absorbed as heat. This activates the reaction to occur. Since it absorbs the heat to start the reaction, then it can be classified as an endothermic reaction.

When plants convert sunlight into chemical energy, it absorbs the sunlight as a light energy on its chlorophyll. This is where photosynthesis occur. This then results to the chlorophyll reacting with the carbon dioxide, water and the energy which results to the production of oxygen and glucose.

So, this explains the answer.

7 0

2 years ago

There are two identical, positively charged conducting spheres fixed in space. The spheres are 40.4 cm apart (center to center)

Nadya [2.5K]

Answer:

$q_1=5.64\times 10^{-7}\ \text{C}$ and $q_2=2.32\times 10^{-6}\ \text{C}$

Explanation:

$F_1=0.072\ \text{N}$

$F_2=0.115\ \text{N}$

r = Distance between shells = 40.4 cm

$q_1$ and $q_2$ are the charges

$k$ = Coulomb constant = $8.99\times10^{9}\ \text{Nm}^2/\text{C}^2$

Force is given by

$F_1=\dfrac{kq_1q_2}{r^2}\\\Rightarrow q_1q_2=\dfrac{F_1r^2}{k}\\\Rightarrow q_1q_2=\dfrac{0.072\times 0.404^2}{8.99\times 10^{9}}\\\Rightarrow q_1q_2=1.307\times 10^{-12}\\\Rightarrow q_1=\dfrac{1.307\times 10^{-12}}{q_2}$

$F_2=\dfrac{kq^2}{r^2}\\\Rightarrow q=\sqrt{\dfrac{F_2r^2}{k}}\\\Rightarrow q=\sqrt{\dfrac{0.115\times 0.404^2}{8.99\times 10^{9}}}\\\Rightarrow q=1.44\times 10^{-6}\ \text{C}$

$q=\dfrac{q_1+q_2}{2}\\\Rightarrow q_1+q_2=2q\\\Rightarrow q_1+q_2=2\times1.44\times 10^{-6}\\\Rightarrow q_1+q_2=2.88\times 10^{-6}$

Substituting the above value of $q_1$ we get

$\dfrac{1.307\times 10^{-12}}{q_2}+q_2=2.88\times 10^{-6}\\\Rightarrow q_2^2-2.88\times 10^{-6}q_2+1.307\times 10^{-12}=0\\\Rightarrow \frac{-\left(-0.00000288\right)\pm \sqrt{\left(-0.00000288\right)^2-4\times \:1\times \:1.307\times 10^{-12}}}{2\times \:1}\\\Rightarrow q_2=2.32\times 10^{-6}, 5.64\times 10^{-7}$

$q_1=\dfrac{1.307\times 10^{-12}}{q_2}=\dfrac{1.307\times 10^{-12}}{2.32\times 10^{-6}}\\\Rightarrow q_1=5.63\times 10^{-7}$

$q_1=\dfrac{1.307\times 10^{-12}}{q_2}=\dfrac{1.307\times 10^{-12}}{5.64\times 10^{-7}}\\\Rightarrow q_1=2.32\times 10^{-6}$

Since we know $q_1$

$q_1=5.64\times 10^{-7}\ \text{C}$ and $q_2=2.32\times 10^{-6}\ \text{C}$ .

5 0

2 years ago

Because cosmic distances are so vast, astronomers use light-years as their unit of distance. One light-year is defined as ______

8090 [49]

Answer:

Because cosmic disaster are so vast, astronomers use light-years as their unit of distance. One light-year is defined as the distance a beam of light travels in one year. The nearest star is a little more than 4.37 light-years away from us. When we see light from a galaxy 2 million light-years away, it has taken 2 million Earth years to reach us. Light from the Sun takes approximately 8.4269 minutes to reach us

Explanation:

i) One light-year is defined as the distance a light beam travels in a time of one Earth year. One light year is equivalent to 6 × 10¹² miles or 9.7 × 10¹² km

ii) The distance to the nearest star = 4.37 light-years

iii) When a star located in a galaxy that is 2.3 million light years away is seen, it has taken 2.3 million light years to reach us

iv) The distance of the Sun to the Earth = 151.58 million kilometers

The speed of light, c = 299792.458 km/s

The time it will take light to reach us from the Sun, 't', is given as follows;

t = 151.58 × 10⁶ km/(299792.458 km/s) ≈ 8.4269 minutes.

7 0

2 years ago