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elena-14-01-66 [18.8K]
3 years ago
5

When a person wearing a helmet rides a bicycle, the helmet experiences which type of friction?

Physics
2 answers:
Vika [28.1K]3 years ago
7 0

Answer:

B.)Static

Hope I helped

vodomira [7]3 years ago
3 0

Answer:

B

Explanation:

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What is the purpose of chloroplasts, and why do you think it is missing from the root hair cell?
Karolina [17]

Explanation:

Mitochondria are essential parts of many eukaryotes, but they are useless without oxygen. Therefore, chloroplasts are extremely important. They produce breathable air for life. Root hairs are seen to not have chloroplasts as their job is to collect water and nutrients.

<h2><em><u>BRAINILIEST</u></em><em><u> </u></em><em><u>PLEASE</u></em><em><u> </u></em></h2>
8 0
3 years ago
Can someone help?
laila [671]

Answer:

i) 21 cm

ii) At infinity behind the lens.

iii) A virtual, upright, enlarged image behind the object

Explanation:

First identify,

object distance (u) = 42 cm (distance between  object and lens, 50 cm - 8 cm)

image distance (v) = 42 cm (distance between  image and lens, 92 cm - 50 cm)

The lens formula,

\frac{1}{v} -\frac{1}{u} =\frac{1}{f}

Then applying the new Cartesian sign convention to it,

\frac{1}{v} +\frac{1}{u} =\frac{1}{f}

Where f is (-), u is (+) and  v is (-) in  all 3  cases. (If not values with signs have to considered, this method that need will not arise)

Substituting values you get,

i) \frac{1}{42} +\frac{1}{42} =\frac{1}{f}\\\frac{2}{42} =\frac{1}{f}

f = 21 cm

ii) u =21 cm, f = 21 cm v = ?

Substituting in same equation\frac{1}{v} =\frac{1}{21} =\frac{1}{21} \\\\\frac{1}{v} = 0\\

  v ⇒ ∞ and image will form behind the lens

iii) Now the object will be within the focal length of the lens. So like in the attachment, a virtual, upright, enlarged image behind the object.

7 0
3 years ago
O professor Hosney, levou os alunos da segunda série ao laboratório para realizar um experimento. Pegou um recipiente de capacid
givi [52]

Answer:

The temperature beyond which the substance overflows the container is 86.23°C.

Explanation:

English Translation

Professor Hosney took the second grade students to the laboratory to perform an experiment. He took a 1000ml capacity container at a temperature of 68oF and poured 980 ml of a substance at 20oC into it. While placing the set to heat, he consulted a table where he found the volumetric expansion coefficient of the substance, 4 x 10-4 ºC-1 and the linear expansion coefficient of the container material, 3 x 10-5 ºC-1. Hosney then asked students to determine the temperature from which the substance would overflow. A student then asked, what is the melting temperature of the substance, and the teacher answered promptly 290.8 K. What is the temperature from which the substance will overflow?

Solution

The change in volume of a substance is given as

ΔV = γV₀(ΔT)

where

γ = coefficient of volume expansion

V₀ = Initial volume

(ΔT) = change in temperature.

At the temperature where the substance will overflow, the volume of the substance and the container will both be the same.

Let this temperature be T.

For the substance,

γ = coefficient of volume expansion = (4 × 10⁻⁴) °C⁻¹

V₀ = Initial volume = 980 mL

(ΔT) = change in temperature = (T - 20)

We will still leave ΔT as ΔT

ΔV₁ = (4 × 10⁻⁴) × 980 × ΔT

ΔV₁ = 0.392 ΔT

New volume of the substance at that temperature = V₀ + ΔV₁ = 980 + 0.392ΔT

For the container

γ = coefficient of volume expansion = 3 × coefficient of linear expansion = 3 × (3 × 10⁻⁵) °C⁻¹ = (9 × 10⁻⁵) °C⁻¹

V₀ = Initial volume = 1000 mL

(ΔT) = change in temperature = (T - 20) (note that 68°F = 20°C)

We will still leave ΔT as ΔT

ΔV₂ = (9 × 10⁻⁵) × 1000 × ΔT

ΔV₂ = 0.09 ΔT

New volume of the container at that temperature = V₀ + ΔV₂ = 1000 + 0.09 ΔT

At the temperature where overflow occurs, the two volumes are initially first the same.

980 + 0.392ΔT = 1000 + 0.09 ΔT

0.392ΔT - 0.09ΔT = 1000 - 980

0.302ΔT = 20

ΔT = (20/0.302) = 66.23°C

T - 20° = 66.23°

T = 66.23 + 20 = 86.23°C

The temperature beyond which the substance overflows the container is 86.23°C.

Hope this Helps!!!

8 0
3 years ago
A spool of thread, free to unwind, is on a horizontal surface (with friction) and pulled directly upward (+y) at all times. The
k0ka [10]

Answer:

The Correct Answer is "D"

Explanation:

For Detail of this answer Please see the attached file.

6 0
3 years ago
And explosion occur 17 km away the time it takes for it sound to reach your ears traveling at 340 m/s is
Mrrafil [7]

Answer:

<h3>t = 100secs</h3>

Explanation:

The following data

Distance x = 17km = 17000m

Speed v = 340m/s

Using the formula to get the time;

2x = vt

t = 2x/v

t = 2(17000)/340

t = 34000/340

t = 100secs

<em>Hence it takes 100seconds for the sound to reach your ears</em>

6 0
3 years ago
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