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3 years ago

John stretched while his muscles were cold. Which negative effect could occur?

Physics

2 answers:

Ede4ka [16]3 years ago

5 0

Answer:

The answer for Plato is C.

Genrish500 [490]3 years ago

3 0

<h3><u>Answer;</u></h3>

C) He could injure or pull a muscle.

<h3><u>Explanation</u>;</h3>

<em><u>When muscles are stretched the muscle fibers are temporary lengthened. Muscles have a unique ability to undergo contraction and lengthening since they are elastic.</u></em>
<em><u>When the muscles are warm they are more elastic, therefore, warming up the muscles is very important for the purpose of avoiding injuries.</u></em> Ir is important to engage in moderate cardiovascular warm-up prior to stretching, which increases the blood flow to the active and thus avoiding injuries to the muscles.
Stretching muscles when they are cold may bring injuries or cause muscle pulls, which are painful.

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A school bus takes 0.53 hours to reach the school from your house. If the average speed of the bus is 19km/h, what is the displa

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D = v*t= 19*0,53 = 10.07 km

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2 years ago

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If you touch the two terminals of a power supply with your two fingertips on opposite hands, the potential difference will produ

LiRa [457]

Answer:

Yes the body will receive a dangerous shock in both cases.

Explanation:

Different parts of the body has different resistance. skin has the high resistance as compared to other organs of the body.

Dry skin has high resistance than wet skin this is because water is relatively good conductor of electricity, it adds parallel path to the current flow and hence reduces skin resistance.

Dry hands body has approximately 500 kΩ resistance and if 120 V electricity supply current received will be:

I = V/R= 120/ 500*10^3

I= 0.24 mA

Even the current seems is much lower than the safe zone but this is the case in case of DC voltage in case of AC voltage the body will receive a shock this is because the skin pass more current when the voltage is changing i.e. AC.

Similarly for wet hands body resistance is 1 kΩ. so the current through the body seems to be:

I = 120 / 1000

I = 12 mA

The current is higher than safe zone so the body will receive a dangerous shock.

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3 years ago

Pure silicon contains approximately 1.0 X 1016 free electrons per cubic meter. (

Margarita [4]

A. The formula for mean free time is:

t = V/(4π√2 r²vN)
where
N = 1×10¹⁶ molecules (per m³)
V = 1 m³
r = 111×10⁻⁷m (atomic radius of silicon)

Let's solve for v first:
v = √(3RT/M) = √(3(8.314 m³·Pa/mol·K)(25 + 273 K)/28.1 g/mol Si)
v = 16.26 m/s

t = (1 m³)/(4π√2 (111×10⁻⁷m)²(16.26 m/s)(1×10¹⁶ molecules))
<em>t = 2.81×10⁻9 s</em>

<em>Pure silicon has a high resistivity relative to copper because copper is a conductor, while silicon is a semi-conductor. </em>

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3 years ago

Bicycle A with mass 40 Kg is traveling with a velocity of 4 m/s and Bicycle B with mass 20 Kg is traveling with a velocity of 2m

andrew-mc [135]

Answer:

bicycle A has a greater K.E.

Explanation:

K.E = 1/2mv²

bicycle A = 1/2 × 40 × 4² = 320J

bicycle B = 1/2 × 20 × 2² = 100J

bicycle A has a greater K.E. because it has bigger mass and moves with faster velocity

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2 years ago

A concrete column has a diameter of 380 mm and a length of 2.6 m . if the density (mass/volume) of concrete is 2.45 mg/m3, deter

grigory [225]

The volume of the column is

(π) · (r²) · (length) =

(π) · (0.19 meter)² · (2.6 meters) =

(π) · (0.036 m²) · (2.6 m) =

0.294 m³ .

The density is 2,450 kg/m³ (VERY very dense, heavy concrete)

so the weight of the column is (mass)·(gravity) or

(density) · (volume) · (gravity) =

(2,450 kg/m³) · (0.294 m³) · (9.81 m/s²) =

(2,450 · 0.294 · 9.81) (kg · m³· m) / (m³ · s²) =

7,066 kg-m/s² = 7,066 Newtons .

But 9.81 Newtons = 2.20462 pounds on Earth (the weight of 1 kilogram of mass), so we have

(7,066 N) · (2.205 pound/9.81 N) =

(7,066 · 2.205 / 9.81) pounds =

1,588 pounds .

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2 years ago