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2 years ago

what is the main difference between a substance going through a physical change and one going through a chemical ?

2 answers:

4 0

Answer: Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.

Ainat [17]2 years ago

3 0

Answer: Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.

Explanation:

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"a 10 kg rock is pushed off the edge of a bridge 50 meters above the ground. what was the kinetic energy of the rock at the midw

valentinak56 [21]

Let's call h the initial height of the rock (h=50 m, the height of the bridge).

Initially, the rock has only gravitational potential energy, which is given by
$U_i=mgh$
where m=10 kg is the mass of the rock while g is the gravitational acceleration. So, the total mechanical energy of the rock at this point is
$E_i = U_i = mgh=(10 kg)(9.81 m/s^2)(50 m)=4905 J$

At midway point of its fall, its height is $\frac{h}{2}$ , so its potential energy is
$U_f = mg \frac{h}{2} = (10 kg)(9.81 m/s^2)(25 m)=2452.5 J$
But now the rock is also moving by speed v, so it also has kinetic energy:
$K_f = \frac{1}{2}mv^2$
So the total energy at the midway point of the fall is
$E_f = U_f + K_f$ (1)

The mechanical energy must be conserved, so $E_i = E_f$ , so we can rewrite (1) and solve it to find the kinetic energy of the rock at midway point of its fall:
$E_i = U_f + K_f$
$K_f = E_i - U_f = 4905 J - 2452.5 J=2452.5 J$

8 0

3 years ago

Name two offensive strategies that can be utilized in the game of baseball

Elden [556K]

Ans: In team offensive strategy, the baseball coach or manager may make certain calls based on the game situation. One play is called ht hit-and-run. This is case where a base runner starts running as soon as the pitcher throws the pitch. The batter is then supposed to try and make contact with the ball.

8 0

3 years ago

How does inertia explain why it is difficult to stop a moving skateboard?

My name is Ann [436]

Answer:

(Example Person) has to push hard to get the skateboard started, but once it begins moving, it takes much less effort to keep it rolling over the smooth, flat pavement. In fact, if (Example Person) tries to stop the rolling skateboard, it may take as much effort to stop it as it did to start it rolling in the first place.

Explanation:

Hope this helps :)

6 0

2 years ago

Which statement about covalent bonds is true

g100num [7]

In covalent bonds the atoms share electrons.

7 0

3 years ago

Read 2 more answers

A mole of a monatomic ideal gas at point 1 (101 kPa, 5 L) is expanded adiabatically until the volume is doubled at point 2. Then

Paha777 [63]

Answer:

(a). Check attachment.

(b). 280.305 J.

(c). 31.81 kpa; 38.26K.

(d). 24.05K.

(e). 24.05k; 40kpa.

(f). -138.6J.

Explanation:

(a). Kindly check the attached picture for the diagram showing the four process.

1 - 2 = adiabatic expansion process.

2 - 3 = Isochoric process.

3 - 4 = isothermal process.

4 - 1 = isochoric process.

(b). Recall that the process from 1 to is an adiabatic expansion process.

NB: b = 5/3 for a monoatomic gas.

Then, the workdone = (1/ 1 - 1.66) [ (p1 × v1^b)/ v2^b × v2 - (p1 × v1)].

= ( 1/ 1 - 5/3) [ (101 × 5^5/3) × 10^1 -5/3] - 101 × 5.

Thus, the workdone = 280.305 J.

(c). P2 = P1 × V1^b/ V2^b = 101 × 5^5/3/ 10^5/3 = 31.81 kpa.

T2 = P2 × V2/ R × 1 = 31.81 × 10/ 8.324 = 38.36k.

(d). The process 2 - 3 is an Isochoric process, then;

T3 = T2/P2 × P3 = 38.26/ 31.82 × 20 = 24.05K.

(e). The process 3 - 4 Is an isothermal process. Then, the temperature at 4 will be the same temperature at 3. Tus, we have the temperature; point 3 = point 4 = 24.05k.

The pressure can be determine as below;

P4 = P3 × V3/ V4 = 20 × 10/ 5 = 200/ 5 = 40 kpa.

(f) workdone = xRT ln( v4/v3) = 1 × 8.314 × 24.05 × ln (5/10) = - 138.6 J

6 0

3 years ago