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3 years ago

Mason notices that his boat sinks lower into the water in a freshwater lake than in the ocean. What could explain this?

Physics

2 answers:

suter [353]3 years ago

5 0

Answer

D. Salt water is denser than freshwater.

Explanation

A boat is able to float on water because it experiences an upthrust upwards.

The magnitude of the upthrust depends on the density of the liquid.

When the liquid is denser the boat will experience a great upthrust as compared to when in a less dense liquid.

If the boat sinks lower in the freshwater than in salty water, then Salt water is more dense than freshwater.

Ludmilka [50]3 years ago

5 0

Answer: D) Salt water is more dense than freshwater.

Explanation: Suppose that you have a glass of water, and you put a little amount of salt in it and mix it.

Now you may see that there is more matter in the glass (the volume of the solution inside the glass also may increase, but not in an appreciable magnitude compared with the increase in mass). And you may know, the density is calculated:

Density = Mass/volume

So if you have more mass in the same volume, this means that the density increases.

And is easier to float in a denser medium than in a low density medium (is easier to float in honey than in water, for example)

So if the medium if denser, the boat will float more easily.

Then the right answer is option D: Salt water is more dense than freshwater

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#1 Not sure where to start. This is for AP Physics!

yaroslaw [1]

First,

$\rho=\dfrac mV$

where $\rho$ is density, $m$ is mass, and $V$ is volume. We can compute the volume of the roll:

$2.7\,\dfrac{\mathrm g}{\mathrm{cm}^3}=\dfrac{1275\,\mathrm g}V$

$\implies V\approx472.22\,\mathrm{cm}^3\approx4.72\,\mathrm m^3$

When the roll is unfurled, the aluminum will be a rectangular box (a very thin one), so its volume will be the product of the given area and its thickness $x$ . Note that we're assuming the given area is not the actual total surface area of the aluminum box, but just the area of the largest face (i.e. the area of one side of the unrolled sheet of aluminum).

So we have

$V=Ax$

where $A$ is the given area, so

$4.72\,\mathrm m^3=\left(18.5\,\mathrm m^2\right)x$

$\implies x\approx0.255\,\mathrm m=255\,\mathrm{mm}$

If we're taking significant digits into account, the volume we found would have been $V=470\,\mathrm m^3$ , in turn making the thickness $x=250\,\mathrm{mm}$ .

8 0

3 years ago

A truck is traveling at 2.0 m/s. It slows to a stop at a constant rate over 3.00 s. How far does the car travel during those 3.0

earnstyle [38]

Answer:

During those 3.00 seconds before stopping, the car travels a distance of 6 m.

Explanation:

The simple rule of three is a tool that is used to quickly solve problems, where three pieces of information must be known, and one of them operates as an unknown to be known.

Two magnitudes are directly proportional if one magnitude increases the other also does it, and if the magnitude decreases the other in the same way.

Being a, b and c known data and x the unknown, the value that we want to know, the rule of three when the magnitudes are directly proportional is applied as follows:

a ⇒ b

c ⇒ x

So: $x=\frac{c*b}{a}$

In this case, knowing that a truck travels at 2 m/s, the rule of three applies as follows: if in 1 second the truck travels 2 m, in 3 seconds how much distance does it travel?

$distance=\frac{3 s*2 m}{1 s}$

distance= 6 m

During those 3.00 seconds before stopping, the car travels a distance of 6 m.

8 0

3 years ago

1. The gravitational force acting on a falling body and its weight is constant. But the law of universal gravitation tells us th

vagabundo [1.1K]

It's not so much a "contradiction" as an approximation. Newton's law of gravitation is an inverse square law whose range is large. It keeps people on the ground, and it keeps satellites in orbit and that's some thousands of km. The force on someone on the ground - their weight - is probably a lot larger than the centripetal force keeping a satellite in orbit (though I've not actually done a calculation to totally verify this). The distance a falling body - a coin, say - travels is very small, and over such a small distance gravity is assumed/approximated to be constant.

3 0

3 years ago

A satellite is in a circular orbit about the earth (ME = 5.98 x 10^24 kg). The period of the satellite is 1.26 x 10^4 s. What is

Soloha48 [4]

Answer: $V=5839.051m/s$

Explanation:

According to the Third Kepler’s Law of Planetary motion:

$T^{2}=\frac{4\pi^{2}}{GM}a^{3}$ (1)

Where;:

$T=1.26(10)^{4}s$ is the period of the satellite

$G$ is the Gravitational Constant and its value is $6.674(10)^{-11}\frac{m^{3}}{kgs^{2}}$

$M=5.98(10)^{24}kg$ is the mass of the Earth

$a$ is the semimajor axis of the orbit the satllite describes around the Earth (as we know it is a circular orbit, the semimajor axis is equal to the radius of the orbit).