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3 years ago

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Which is a sign of a chemical change? A) Ice cream left at room temperature melts. B) Calcium chloride is dissolved in H2O and d

isappears. C) Paint on a freshly painted wall dries and is no longer sticky. D) When H2S gas is bubbled into a lead acetate solution, a precipitate forms.

2 answers:

Eduardwww [97]3 years ago

7 0

D, because a physical change is when something changes but doesn't change into a new substance. A chemical change is when something changes into a new substance.

Katarina [22]3 years ago

5 0

Chemical change is any change that results in the formation of new chemical substances. (Thanks to google)

This the answer is D

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A ball is thrown vertically upwards from the edge of the cliff and hits the ground at the base of the cliff with a speed of 30 m

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To solve this problem we will apply the linear motion kinematic equations. From the definition of the final velocity, as the sum between the initial velocity and the product between the acceleration (gravity) by time, we will find the final velocity. From the second law of kinematics, we will find the vertical position traveled.

$v = v_0 -gt$

Here,

v = Final velocity

$v_0$ = Initial velocity

g = Acceleration due to gravity

t = Time

At t = 4s, v = -30m/s (Downward)

Therefore the initial velocity will be

$-30 = v_0 -9.8(4)$

$v_0 = 9.2m/s$

Now the position can be calculated as,

$y = h +v_0t -\frac{1}{2}gt^2$

When it has the ground, y=0 and the time is t=4s,

$0 = h+(9.2)(4)-\frac{1}{2} (9.8)(4)^2$

$h = 41.6m$

Therefore the cliff was initially to 41.6m from the ground

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3 years ago

Complete the equation???

soldi70 [24.7K]

Here in nuclear reaction we can say that sum of neutrons and protons in reactant side and product side will be same always

Here mass number on the product side is given to us

so sum of mass number is given as

$A_1 + A_2 = 265 + 1 = 266$

now on the reactant side also the number must be same

$A_1' + A_2' = 58 + x$

now we will have

$58 + x = 266$

$x = 208$

Now number of protons on product side is given as

$P_1 + P_2 = 108 + 0$

now we also know that atomic number of Fe is 26

so now we will have

$P_1' + P_2' = 108$

$26 + P_2' = 108$

$P_2' = 82$

now the equation is given as

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3 years ago

Nadya [2.5K]

1) The mass of the continent is $3.3\cdot 10^{21}kg$

2) The kinetic energy of the continent is 1683 J

3) The speed of the jogger must be 6.57 m/s

Explanation:

1)

The continent can be represented as a slab of size

$d=5850 km = 5.85\cdot 10^6 m$

and depth

$t = 35 km = 3.5\cdot 10^4 m$

So its volume is

$V=d^2 t = (5.85\cdot 10^6)^2(3.5\cdot 10^4)=1.20\cdot 10^{18} m^3$

We also know that the density of the continent is

$\rho = 2750 kg/m^3$

Therefore, we can calculate its mass as:

$m=\rho V=(2750)(1.20\cdot 10^{18})=3.3\cdot 10^{21} kg$

2)

The kinetic energy of the continent is given by

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

where

m is its mass

v is its speed

We have already calculate its mass, while the speed is

v = 3.2 cm/year

We have to convert into SI units first, as follows:

$v=3.2 \frac{cm}{year} \cdot \frac{1}{100 cm/m} \cdot \frac{1}{(365 d/y)(24h/d)(60min/h)(60 s/min)}=1.01\cdot 10^{-9} m/s$

The mass is

$m=3.3\cdot 10^{21} kg$

So, the kinetic energy of the continent is

$K=\frac{1}{2}(3.3\cdot 10^{21})(1.01\cdot 10^{-9})^2=1683 J$

3)

Here we have a jogger having the same kinetic energy of the continent, so

$K=1683 J$

And the kinetic energy of the jogger can be expressed as

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

where

m = 78 kg is the mass of the jogger

v is his speed

We can therefore re-arrange the equation to find the speed of the man, and we get:

$v=\sqrt{\frac{2K}{m}}=\sqrt{\frac{2(1683)}{78}}=6.57 m/s$

Learn more about kinetic energy:

brainly.com/question/6536722

#LearnwithBrainly

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3 years ago

A man runs 800m due north in 110 seconds followed by 400m due suoth in 90 seconds calculate his average speed and his average ve

andrey2020 [161]

Answer:

Average speed is 6m/s

Average velocity is 5.859m/s

Explanation:

Average speed, s = d/t

d is distant

t is time

speed north is 800m and 110s

speed due south is 400m and 90s

Average speed = (800+400) / (110+90)

= 1200/200

=6m/s

Average velocity V = (v + u)/2

v = final velocity

u = initial velocity

V = (7.273 + 4.444)/2 = 11.717/2

V = 5.859m/s

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3 years ago

A scientist is asking you what would happen to Radon-226 (represented by Ra on the graph and 226 is the atomic mass) if instead

ladessa [460]

The sky legit green today

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3 years ago