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3 years ago

Integrated Science- 8th grade science

Physics

2 answers:

Kaylis [27]3 years ago

8 0

Answer:

The answer is option letter B

padilas [110]3 years ago

3 0

Answer:

A. a rigorously tested explanation

Explanation:

B. and D. are out - theories are not opinionated, they are factual
C. is out - not all theories are mathematical
A. is the best choice

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A skateboarder initially has 5 kJ of kinetic energy. As she freewheels along a flat section of path, she does 400 J of work agai

sweet [91]

The final kinetic energy of the skateboarder after she freewheels and did work against friction on the flat section of the path is 4,600 J.

<h3>Conservation of energy</h3>

The final kinetic energy of the stakeboarder is determined by applying the principle of conservation of energy as shown below;

ΔK.E = -W

K.Ef - K.Ei = -W

where;

K.Ef is the final kinetic energy
K.Ei is the initial kinetic energy
W is work done

K.Ef = K.Ei - W

K.Ef = 5,000 J - 400 J

K.Ef = 4,600 J

Thus, the final kinetic energy of the skateboarder is 4,600 J.

Learn more about kinetic energy here: brainly.com/question/25959744

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2 years ago

Which of the following is an example of a main sequence star

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The star is the main sequence

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An atom of an element is electrically neutral because the

lora16 [44]

Answer:

Number of protons equals the number of neutrons

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When are the displacement and acceleration equal to zero for the motion of a mass on a spring?

aliina [53]

Answer:

Option B is the right answer.

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4 years ago

A river flows due east at 1.60 m/s. A boat crosses the river from the south shore to the north shore by maintaining a constant v

Citrus2011 [14]

Answer:

part (a) $v\ =\ 10.42\ at\ 81.17^o$ towards north east direction.

part (b) s = 46.60 m

Explanation:

Given,

velocity of the river due to east = $v_r\ =\ 1.60\ m/s.$
velocity of the boat due to the north = $v_b\ =\ 10.3\ m/s.$

part (a)

River is flowing due to east and the boat is moving in the north, therefore both the velocities are perpendicular to each other and,

Hence the resultant velocity i,e, the velocity of the boat relative to the shore is in the North east direction. velocities are the vector quantities, Hence the resultant velocity is the vector addition of these two velocities and the angle between both the velocities are $90^o$

Let 'v' be the velocity of the boat relative to the shore.

$\therefore v\ =\ \sqrt{v_r^2\ +\ v_b^2}\\\Rightarrow v\ =\ \sqrt{1.60^2\ +\ 10.3^2}\\\Rightarrow v\ =\ 10.42\ m/s.$

Let $\theta$ be the angle of the velocity of the boat relative to the shore with the horizontal axis.

Direction of the velocity of the boat relative to the shore. $\therefore Tan\theta\ =\ \dfrac{v_b}{v_r}\\\Rightarrow Tan\theta\ =\ \dfrac{10.3}{1.60}\\\Rightarrow \theta\ =\ Tan^{-1}\left (\dfrac{10.3}{1.60}\ \right )\\\Rightarrow \theta\ =\ 81.17^o$

part (b)

Width of the shore = w = 300m

total distance traveled in the north direction by the boat is equal to the product of the velocity of the boat in north direction and total time taken

Let 't' be the total time taken by the boat to cross the width of the river. $\therefore w\ =\ v_bt\\\Rightarrow t\ =\ \dfrac{w}{v_b}\\\Rightarrow t\ =\ \dfrac{300}{10.3}\\\Rightarrow t\ =\ 29.12 s$

Therefore the total distance traveled in the direction of downstream by the boat is equal to the product of the total time taken and the velocity of the river $\therefore s\ =\ u_rt\\\Rightarrow s\ =\ 1.60\times 29.12\\\Rightarrow s\ =\ 46.60\ m$

7 0

3 years ago