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3 years ago

How can we tell when forces are acting on an object (science)

1 answer:

4 0

If an object's speed changes, or if it changes the direction it's moving in,
then there must be forces acting on it. There is no other way for any of
these things to happen.

Once in a while, there may be a group of forces (two or more) acting on
an object, and the group of forces may turn out to be "balanced". When
that happens, the object's speed will remain constant, and ... if the speed
is not zero ... it will continue moving in a straight line. In that case, it's not
possible to tell by looking at it whether there are any forces acting on it.

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A motorcyclist drove 7 km at 57km/h and then another 7 km at 81 km/h. What was the average speed?

alex41 [277]

Answer:

The average speed of the car is 66.9 km/h

Explanation:

Here distance covered with the speed 57 km/h=7 km 

distance covered with the speed of 81 km/h=7 km

Average speed is equal to the ratio of total distance to the total time.

total distance= 7 + 7= 14 km

$time= \frac{distance}{speed}$

time taken to cover the first 7 km= 7/57 h

time taken to cover the second part of the journey = 7/81 h

average speed = $14/(7/57+7/81)=(14 \times 57 \times 81)/945=66.9 km/h$ 

Shortcut: 

When equal distances are covered with different speeds average speed=2 ab/(a+b) where a and b are the variable speeds in the phases. 

7 0

3 years ago

The moon Phobos orbits Mars

Soloha48 [4]

Answer:

Explanation:

We are basically needing to solve for the time in the equation d = rt, where d is the distance around Mars (aka the circumference), r is the velocity, and t is time. We need to find the circumference and the velocity. We will begin with the velocity.

Because the gravitational attraction between Phobos and Mars provides the centripetal acceleration necessary to keep Phobos in its (sort of) circular path, the equation we use for this is:

$F_g=F_c$ which says that Force supplied by gravity is equal to the centripetal force. Expanding that:

$\frac{Gm_{Phobos}m_{Mars}}{r^2}=\frac{m_{Phobos}v^2}{r}$

When we move that around mathematically to solve for the velocity value, what we end up with is:

$v=\sqrt{\frac{Gm_{Mars}}{r}$ and filling in:

$v=\sqrt{\frac{(6.67*10^{-11})(6.42*10^{23})}{9.38*10^6} }$ and we get that

v = 2100 m/s

Now for the circumference:

C = 2πr and

C = 2(3.1415)(9.38 × 10⁶) so

C = 5.9 × 10⁷

Putting that all together in the C = vT equation:

5.9 × 10⁷ = 2100T so

T = 2.8 × 10⁴ sec or 7.8 hours

8 0

3 years ago

A speed skater just finished a race. After she crossed the finish line, she coasted to a complete stop. If her initial speed was

romanna [79]

Answer:

5seconds

Explanation:

because she was going through the same time

6 0

2 years ago

compare the numbers of each subatomic particle found in both diagrams and then list what makes hydrogen diffrent from hellium

Cloud [144]

The helium atom is found to contain more particles than the hydrogen atom.

<h3>What is a subparticle?</h3>

An atom is composed of particles and these particles are electrons protons and neutrons. The collective name for these particles is the subatomic particles.

Now we know that the helium atom contains more sub atomic particles than the atom of hydrogen. This is because, the helium atom contains two neutrons and two protons as well as two electrons. On the other hand, the hydrogen atom contains one neutron and one proton as well as one electron.

Thus, the helium atom is found to contain more particles than the hydrogen atom.

Learn more about helium atom:brainly.com/question/4945478

#SPJ1

7 0

1 year ago

Why are the fingers of a human separated by gaps?

OverLord2011 [107]

A.
It's has to do with the human body forming in the womb. It has a long explanation to it, but I hope just writing A helps.

3 0

3 years ago