I cant belive im doing this- i will mark brainliest if this gets answered- mostly correct.

Which of the following is a force or motion that

faltersainse [42]

Answer: this answer is D. That's what I think it is

Explanation:

7 0

2 years ago

find the time taken, if the speed of a train increased from 72 km/hr to 90 km/hr for 234 km. leave your answer in seconds

Airida [17]

Answer:

Time taken = 10400 s

Explanation:

Given:

Initial speed of the train, $u=72\textrm{ km/h}=72\times \frac{5}{18}=20\textrm{ m/s}$

Final speed of the train, $v=90\textrm{ km/h}=90\times \frac{5}{18}=25\textrm{ m/s}$

Displacement of the train, $S=234\textrm{ km}=234\times 1000=234000\textrm{ m}$

Using Newton's equation of motion,

$v - u = at\\a=\frac{v-u}{t}$

Now, using Newton's equation of motion for displacement,

$v^{2}-u^{2}=2aS$

Now, plug in the value of $a=\frac{v-u}{t}$ in the above equation. This gives,

$v^{2}-u^{2}=2\times \frac{v-u}{t}\times S\\(v+u)(v-u)=\frac{2(v-u)S}{t}\\t=\frac{2(v-u)S}{(v+u)(v-u)}\\t=\frac{2S}{v+u}$

Now, plug in 234000 m for $S$ , 25 m/s for $v$ and 20 m/s for $u$ . Solve for $t$ .

$t=\frac{2S}{v+u}\\t=\frac{2\times 234000}{25+20}\\t=\frac{468000}{45}=10400\textrm{ s}$

Therefore, the time taken by the train is 10400 s.

3 0

4 years ago

I need help answering this question in the photo (middle)

GalinKa [24]

I believe it is because of weight if Timmy is larger and bigger than Maria that would mean he would stop slower just because of his bodyweight pushing on the back of the skateboard while Maria is all those skinny and she doesn’t have as much weight as she can go farther

3 0

3 years ago

The law of universal gravitation states that a gravitational force exists between all objects in the universe. This force is dir

Ber [7]

Answer: D. it has been demonstrated to be without exception under certain stated conditions.

Explanation:

A Law is an affirmation (something established) based on repeated long-term observation of a phenomenon that has been studied and verified.

That is: A law is present in all known theories and therefore is considered universal. In addition, a law can not be refuted, nor changed, because its precepts have been proven through various studies.

Unlike theory, which is the set of rules and principles that describe and explain a particular phenomenon and is subject to changes as new evidence emerges that gives meaning to it.

Then, based on what is explained above, the law of universal gravitation is a statement that exists because it was rigorously tested and verified, therefore it can not be refuted.

3 0

3 years ago

?????Help please?????

Sindrei [870]

The correct selections are C, C, B, D, A, B, and A .

6 0

3 years ago