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Sever21 [200]
2 years ago
15

Alan wrote the following examples of changes in substance.

Physics
2 answers:
Anastaziya [24]2 years ago
6 0

Answer:

The correct option is B

Explanation:

A physical change is characterized by the following

  • no new substance is formed
  • easily reversible
  • cannot be represented by a chemical reaction

A chemical change is characterized by the following

  • new substances are formed
  • easily reversible
  • can be represented by a chemical reaction

A camp fire is usually made by burning woods. This process is called combustion, it involves the burning of a substance in oxygen to produce carbon dioxide (CO₂). This is a chemical change because new substance (CO₂) is formed and the ashes formed (after burning) cannot be reversed back to wood.

Plants convert carbon dioxide and water into glucose and oxygen through photosynthesis. This process is also a chemical change because new substances (glucose and oxygen) are formed and the reaction cannot also be easily reversed.

The reaction involved can be represented as  

6CO₂ + 6H₂O ⇒ C₆H₁₂O₆ + 6O₂

Yuliya22 [10]2 years ago
5 0
A campfire being lighted and plants converting carbon-dioxide and water into glucose and oxygen are both forms of chemical change.

Therefore, the answer is:

B. Both are examples of chemical change.
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A champion athlete can produce one horsepower (746 W) for a short period of time. The number of 16-cm-high steps a 70-kg athlete
erastovalidia [21]

Answer:

407 steps

Explanation:

From the question,

P = mgh/t........... Equation 1

Where P = power, m = mass, g = acceleration due to gravity, h = height, t = time.

Make h the subject of the equation

h = Pt/mg............. Equation 2

Given: P = 746 W, t = 1 minute = 60 seconds, m = 70 kg.

Constant: g = 9.8 m/s²

Substitute into equation 2

h = 746(60)/(70×9.8)

h = 44760/686

h = 65.25 m

h = 6525 cm

number of steps = 6525/16

number of steps = 407 steps

6 0
2 years ago
A 40-w lightbulb connected to a 120-v source experiences a voltage surge that produces 132 v for a moment. by what percentage do
andrey2020 [161]
R=U^2/P=120*120/40=360 ohm
P2=U2^2/R=132*132/360=48.4 w
power increase ratio (48.4-40)/40=21%
3 0
2 years ago
Using energy considerations and assuming negligible air resistance, show that a rock thrown from a bridge 20.0 m above water wit
melamori03 [73]

Answer:

Explanation:

Given that,

Height of the bridge is 20m

Initial before he throws the rock

The height is hi = 20 m

Then, final height hitting the water

hf = 0 m

Initial speed the rock is throw

Vi = 15m/s

The final speed at which the rock hits the water

Vf = 24.8 m/s

Using conservation of energy given by the question hint

Ki + Ui = Kf + Uf

Where

Ki is initial kinetic energy

Ui is initial potential energy

Kf is final kinetic energy

Uf is final potential energy

Then,

Ki + Ui = Kf + Uf

Where

Ei = Ki + Ui

Where Ei is initial energy

Ei = ½mVi² + m•g•hi

Ei = ½m × 15² + m × 9.8 × 20

Ei = 112.5m + 196m

Ei = 308.5m J

Now,

Ef = Kf + Uf

Ef = ½mVf² + m•g•hf

Ef = ½m × 24.8² + m × 9.8 × 0

Ef = 307.52m + 0

Ef = 307.52m J

Since Ef ≈ Ei, then the rock thrown from the tip of a bridge is independent of the direction of throw

7 0
2 years ago
A container of nitrogen (an ideal diatomic gas, molecular weight=28) is at a pressure of 2 atm and has a mass density of 1.6 gra
Nikolay [14]

Answer:

Explanation:What is the root-mean-square velocity (vrms) of the center of mass of one of the molecules?

3 0
2 years ago
in physics lab, a cube slides down a frictionless incline as shown in the figure below, and elastically strikes another cube at
Tema [17]
<span>In the physics lab, a cube slides down a frictionless incline as shown in the figure below, check the image for the complete solution:

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3 0
2 years ago
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