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3 years ago

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For an object that floats in a liquid, which of the following statements is true? Group of answer choices The specific gravity o

f the object is greater than or equal to the specific gravity of the liquid. The mass of the object is equal to the mass of liquid displaced.

1 answer:

SVEN [57.7K]3 years ago

8 0

Answer:

Explanation:

Object is Floating in a liquid

weight of object is equal to weight of displaced fluid

i.e.

$\rho _oVg=\rho _mV'g$

i.e. $\rho _oV=mass\ of\ object$

$\rho _mV'=mass\ of\ liquid\ displaced$

where V and V' is the volume of object and volume of object inside the liquid.

therefore mass of liquid displaced must be equal to mass of object

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During an investigation, a scientist heated 123.6 g of copper carbonate till it decomposed to form a black residue. The total ma

zloy xaker [14]

Answer:

See below explanation

Explanation:

The correspondent chemical reaction for copper carbonate decomposed by heat is:

CuCO₃ (s) → CuO (s) + CO₂ (g)

Considering all molar mass (MM) for each element ( we consider rounded numbers) :

MM CuCO₃ = 123 g/mol

MM CuO = 79 g/mol

MM CO₂ = 44 g/mol

Statement mentions that scientis heated 123.6 g of CuCO₃ (almost a MM), until a black residue is obtained, which weights 79.6 g : this solid residue is formed by CuO, and the remaining mass (approximatelly 44 g) belongs to teh second product, this is, CO₂; as it is a gas compund, it is not certainly included on the solid residue.

So, law of conservation mass is true for this case, since: 123.6 g = 79.6 g + 44 g. As explained, on the solid residue, we don not include the 44 g, which "escaped" from our system, since it is a gas compound (CO₂)

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3 years ago

A bungee jumper with mass 65.0 kg jumps from a high bridge. After reaching his lowest point, he oscillates up and down, hitting

ololo11 [35]

Explanation:

It is given that,

Mass of a bungee jumper is 65 kg

The time period of the oscillation is 38 s, hitting a low point eight more times.It means its time period is

$T=\dfrac{38}{8}\\\\T=4.75\ s$

After many oscillations, he finally comes to rest 25.0 m below the level of the bridge.

For an oscillating object, the time period is given by :

$T=2\pi \sqrt{\dfrac{m}{k}}$

k = spring stiffness constant

So,

$k=\dfrac{4\pi ^2m}{T^2}\\\\k=\dfrac{4\pi ^2\times 65}{(4.75)^2}\\\\k=113.43\ N/m$

When the cord is in air,

mg=kx

x = the extension in the cord

$x=\dfrac{mg}{k}\\\\x=\dfrac{65\times 9.8}{113.6}\\\\x=5.6\ m$

So, the unstretched length of the bungee cord is equal to 25 m - 5.6 m = 19.4 m

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3 years ago

Calculate the mass of air in a room 5m × 4m ×2m given that the density of air is 1.3kgm-²

valentina_108 [34]

32.5 kg of air

Explanation:

To calculate the mass of the air, we use the density formula:

density = mass / volume

mass = density × volume

density of air = 1.3 kg/m³

volume = 5 × 3 × 2 = 25 m³

mass of the air = 1.3 kg/m³ × 25 m³

mass of the air = 32.5 kg

Learn more about:

density

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3 years ago

a vector has an x-component of 19.5m and a y-component of 28.4m. Find the magnitude and direction of the vector

Delicious77 [7]

Answer:

magnitude=34.45 m

direction= $55.52\°$

Explanation:

Assuming the initial point P1 of this vector is at the origin:

P1=(X1,Y1)=(0,0)

And knowing the other point is P2=(X2,Y2)=(19.5,28.4)

We can find the magnitude and direction of this vector, taking into account a vector has a initial and a final point, with an x-component and a y-component.

For the magnitude we will use the formula to calculate the distance $d$ between two points:

$d=\sqrt{{(Y2-Y1)}^{2} +{(X2-X1)}^{2}}$ (1)

$d=\sqrt{{(28.4 m - 0 m)}^{2} +{(19.5 m - 0m)}^{2}}$ (2)

$d=\sqrt{1186.81 m^{2}}$ (3)

$d=34.45 m$ (4) This is the magnitude of the vector

For the direction, which is the measure of the angle the vector makes with a horizontal line, we will use the following formula:

$tan \theta=\frac{Y2-Y1}{X2-X1}$ (5)

$tan \theta=\frac{24.8 m - 0m}{19.5 m - 0m}$ (6)

$tan \theta=\frac{24.8}{19.5}$ (7)

Finding $\theta$ :

$\theta= tan^{-1}(\frac{24.8}{19.5})$ (8)

$\theta= 55.52\°$ (9) This is the direction of the vector

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3 years ago

A 30 g horizontal metal bar, 13 cm long, is free to slide up and down between two tall, vertical metal rods that are 13 cm apart

natita [175]

Answer:

Terminal speed, v = 6901.07 m/s

Explanation:

It is given that,

Mass of the horizontal bar, m = 30 g = 0.03 kg

Length of the bar, l = 13 cm = 0.13 m

Magnetic field, $B=5.5\times 10^{-2}\ T$

Resistance, R = 1.2 ohms

We need to find the terminal speed oat which the bar falls. When terminal speed is reached,

Force of gravity = magnetic force

$mg=ilB$ ..................(1)

i is the current flowing

l is the length of the rod

Due to the motion in rods, an emf is induced in the coil which is given by :

$E=Blv$ , v is the speed of the bar

$iR=Blv$

$i=\dfrac{Blv}{R}$

Equation (1) becomes,

$mg=\dfrac{B^2l^2v}{R}$

$v=\dfrac{mgR}{B^2l^2}$

$v=\dfrac{0.03\times 9.8\times 1.2}{(5.5\times 10^{-2})^2(0.13)^2}$

v = 6901.07 m/s

So, the terminal speed at which the bar falls is 6901.07 m/s. Hence, this is the required solution.

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3 years ago