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SVETLANKA909090 [29]
3 years ago
13

Given the hypothesis that the element zinc prevents cancer, which of the following procedures BEST exemplifies the nature of sci

entific investigation?
A- Analyze zinc, looking for different forms

B- Do research on zinc and its uses throughout history to determine if there is evidence that zinc prevents incidence of cancer


C- Rely on testimony of friends and relatives, as well as conduct a survey to see if there is a concentration of cancer in the people not taking zinc supplements


D- Give zinc supplements to a group of rats and not to another group. After a period of time, determine if there is a higher incidence of cancer in the control group​
Physics
1 answer:
lidiya [134]3 years ago
4 0

Answer:D

Explanation: i found the answer in an answer key!

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It is mainly used to give facts about living organisms

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You pull your little sister across a flat snowy field on a sled. Your sister plus the sled have a mass of 22 kg. The rope is at
kati45 [8]

Answer:

Explanation:

mass of sled, m = 22 kg

Force of pull, F = 31 N

distance move, d = 53 m

Angle between force and distance, θ = 40°

The formula for the work done is

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7 0
3 years ago
2. While standing near a bus stop, a student hears a distant horn beeping. The frequency emitted by the horn is 440 Hz. The bus
jarptica [38.1K]

Given Information:

Frequency of horn = f₀ = 440 Hz

Speed of sound = v = 330 m/s

Speed of bus = v₀ = 20 m/s

Answer:

Case 1. When the bus is crossing the student = 440 Hz

Case 2. When the bus is approaching the student = 414.9 Hz

Case 3. When the bus is moving away from the student = 468.4 Hz

Explanation:

There are 3 cases in this scenario:

Case 1. When the bus is crossing the student

Case 2. When the bus is approaching the student

Case 3. When the bus is moving away from the student

Let us explore each case:

Case 1. When the bus is crossing the student:

Student will hear the same frequency emitted by the horn that is 440 Hz.

f = 440 Hz

Case 2. When the bus is approaching the student

f = f₀ ( v / v+v₀ )

f = 440 ( 330/ 330+20 )

f = 440 ( 330/ 350 )

f = 440 ( 0.943 )

f = 414.9 Hz

Case 3. When the bus is moving away from the student

f = f₀ ( v / v+v₀ )

f = 440 ( 330/ 330-20 )

f = 440 ( 330/ 310 )

f = 440 ( 1.0645 )

f = 468.4 Hz

6 0
3 years ago
The eficiency of a <br> simple machine can never be 100% why?​
Kitty [74]

Answer:

Systems always tend toward a state of decreasing order unless more energy is provided into the system to counteract this tendency.

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3 years ago
Maurice directs a beam of light on a sheet of glass at an angle of 51°. What is the angle of refraction in the glass? The refrac
iVinArrow [24]
Maurice directs a beam of light on a sheet of glass at an angle of 51°. The refractive index of glass is <span>1.46. </span>The angle of refraction in the glass is 29 degrees. The answer is letter B.
4 0
3 years ago
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