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3 years ago

A ring made of gold is heated and then hammered into a flat, coin-like shape. Is this a physical change? Explain.

2 answers:

7 0

Yes. a physical change is only modifying the structure of it.

a chemical change is permanently changing something.

cutting cheese into slices is a physical change

cooking an egg is a chemical change

andre [41]3 years ago

6 0

Yes,
this would be a physical change because the chemical composition is not being effected. When you change the shape of gold, it will remain gold but have a different look.

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Sandi believes that people who eat at McDonald's are overweight, so she decides to do a naturalistic observation of people who e

lubasha [3.4K]

Answer:

observer bias

Explanation:

Based on the information provided within the question the thing that should concern us the most about Sandi's observations is Observer Bias. This term refers to the tendency of a researcher to see what they want as opposed to what is actually happening. This can be said because of Sandi's belief that McDonald clients are all overweight, by having this belief before actually having come to this conclusion with a series of tests, it might lead her to believe this to be true regardless of what she observes during the experiment.

I hope this answered your question. If you have any more questions feel free to ask away at Brainly.

6 0

3 years ago

O que é cena fone de luz na visão da fisica

yulyashka [42]

Me don’t speak spanish

4 0

3 years ago

(a) According to Hooke's Law, the force required to hold any spring stretched x meters beyond its natural length is f(x)=kx. Sup

KengaRu [80]

Answer:

a) The work required to stretch the spring from 20 centimeters to 25 centimeters is 0.313 joules, b) The area of the region enclosed by one loop of the curve $r(\theta) = 2\cdot \sin 5\theta$ is $4\pi$ .

Explanation:

a) The work, measured in joules, is a physical variable represented by the following integral:

$W = \int\limits^{x_{f}}_{x_{o}} {F(x)} \, dx$

Where

$x_{o}$ , $x_{f}$ - Initial and final position, respectively, measured in meters.

$F(x)$ - Force as a function of position, measured in newtons.

Given that $F = k\cdot x$ and the fact that $F = 25\,N$ when $x = 0.3\,m - 0.2\,m$ , the spring constant ( $k$ ), measured in newtons per meter, is:

$k = \frac{F}{x}$

$k = \frac{25\,N}{0.3\,m-0.2\,m}$

$k = 250\,\frac{N}{m}$

Now, the work function is obtained:

$W = \left(250\,\frac{N}{m} \right)\int\limits^{0.05\,m}_{0\,m} {x} \, dx$

$W = \frac{1}{2}\cdot \left(250\,\frac{N}{m} \right)\cdot [(0.05\,m)^{2}-(0.00\,m)^{2}]$

$W = 0.313\,J$

The work required to stretch the spring from 20 centimeters to 25 centimeters is 0.313 joules.

b) Let be $r(\theta) = 2\cdot \sin 5\theta$ . The area of the region enclosed by one loop of the curve is given by the following integral:

$A = \int\limits^{2\pi}_0 {[r(\theta)]^{2}} \, d\theta$

$A = 4\int\limits^{2\pi}_{0} {\sin^{2}5\theta} \, d\theta$

By using trigonometrical identities, the integral is further simplified:

$A = 4\int\limits^{2\pi}_{0} {\frac{1-\cos 10\theta}{2} } \, d\theta$

$A = 2 \int\limits^{2\pi}_{0} {(1-\cos 10\theta)} \, d\theta$

$A = 2\int\limits^{2\pi}_{0}\, d\theta - 2\int\limits^{2\pi}_{0} {\cos10\theta} \, d\theta$

$A = 2\cdot (2\pi - 0) - \frac{1}{5}\cdot (\sin 20\pi-\sin 0)$

$A = 4\pi$

The area of the region enclosed by one loop of the curve $r(\theta) = 2\cdot \sin 5\theta$ is $4\pi$ .

5 0

2 years ago

At the train station, you notice a large horizontal spring at the end of the track where the train comes in. This is a safety de

e-lub [12.9K]

Assume a maximum stopping acceleration of g/2 where g is acceleration due to gravity.

Answer:

2.99 m/s

Explanation:

Stopping distance, s = 3 ft = 0.914 m

final velocity, v = 0

a = g/2 = 4.9 m/s²

Use third equation of motion:

$v^2-u^2 = 2as$

substitute the values to find the speed of train:

$0 -u^2 = 2\times -4.9 \times 0.914 \\u^2=8.96 \\u=2.99 m/s$

6 0

3 years ago

Why is it important to understand forces?

yanalaym [24]

If people never learned forces, there would be a major gap in the world and how it works, let alone in physics...
as much as you don't wanna admit it, force is everywhere and you see it if not use it EVERY day in your life, something as simple as driving a car down the street or too school, your using force of your wheels to move your car, which is moving you

3 0

3 years ago