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3 years ago

Why is chopping carrots a physical change ?

2 answers:

7 0

Answer: Chopping or cutting is a physical change. Any change in size and shape is attributed as physical change. There is no formation of a new substance after chopping and the molecular component of the carrots stays the same. Therefore it is a physical change.

Explanation:

astra-53 [7]3 years ago

5 0

Answer: Chopping carrots is a chemical change because you aren't changing the property its substance, you are just chopping it up, there is no new substance being formed.

Explanation:

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The drag force pushes opposite your motion as you ride a bicycle. If you double your speed, what happens to the drag force?

timurjin [86]

Answer: The drag force goes up by a factor of 4

Explanation:

The Drag Force equation is:

$F_{D}=\frac{1}{2}C_{D}\rho A_{D}V^{2}$ (1)

Where:

$F_{D}$ is the Drag Force

$C_{D}$ is the Drag coefficient, which depends on the material

$\rho$ is the density of the fluid where the bicycle is moving (air in this case)

$A_{D}$ is the transversal area of the body or object

$V$ the bicycle's velocity

Now, if we assume $C_{D}$ , $\rho$ and $A_{D}$ do not change, we can rewrite (1) as:

$F_{D}=C.V^{2}$ (2)

Where $C$ groups all these coefficients.

So, if we have a new velocity $V_{n}$ , which is the double of the former velocity:

$V_{n}=2V$ (3)

Equation (2) is written as:

$F_{D}=C.V_{n}^{2}=C.(2V)^{2}$

$F_{D}=4CV^{2}$ (4)

Comparing (2) and (4) we can conclude the Drag force is four times greater when the speed is doubled.

7 0

2 years ago

1. A 4-N force is used to move an object 2 m in 10 s. Which of the following is the power generated while moving the object?

guajiro [1.7K]

Power is the work done per unit time. Therefore,

$\begin{gathered} p=\frac{w}{t} \\ \text{where} \\ w=\text{work done} \\ t=\text{time} \end{gathered}$

Therefore,

$\begin{gathered} \text{work done=fd} \\ f=force=4N \\ d=\text{displacement}=2m \\ t=2\sec s \\ p=\frac{fd}{t}=\frac{4\times2}{10}=\frac{8}{10}=0.8watts \end{gathered}$

4 0

1 year ago

Which of the following is composed of only one kind of atom?

UNO [17]

Answer:

An element is a pure substance and is made of only one type of atom; it cannot be broken down into a simpler substance.

3 0

2 years ago

If a baseball has a zero velocity at some instant, is the acceleration of the baseball necessarily zero at that time? Explain -

ipn [44]

Answer:

No, not necessarily

Explanation:

If an object is moving with an acceleration that causes its speed to be reduced, there will be a moment in which it reaches v = 0, but this doesn't necessarily mean that the acceleration isn't acting anymore. If the object continues its movement with the same acceleration, it's velocity will become negative.

An example of an object that has zero velocity but non-zero acceleration:

If you throw an object in the air with a certain velocity, it will move vertically, reducing its velocity in a 9,8 $m/s^{2}$ rate (which is the acceleration caused by gravity). At a certain point, the object will reach its maximum height, and will start to fall. In the exact moment that it reaches the maximum height, before it starts falling, its velocity is zero, but gravity is still acting on the object (this is the reason why it starts falling instead of just being stopped at that point). Therefore, at that point, the object has zero velocity but an acceleration of 9,8 $m/s^{2}$ .

3 0

2 years ago

Mấy bạn việt nam giúp mình với. cần gấp quá

Basile [38]

Saying english so we can help u

6 0

2 years ago