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3 years ago

If We Start With 48 Atoms Of A Radioactive Substance, How Many Would Remain After One Half-life?

1 answer:

4 0

One half-life produces (1/2) of the decaying substance.

There would still be 48 atoms. But 24 would have thrown off
particles from their nucleuses, and only 24 would still be radioactive.

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A woman can lift barrels a vertical distance of 1 meter or can roll them up a 2-meter long ramp to the same elevation. If she us

olchik [2.2K]

Answer:

answer is 1/2 as much force required

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2 years ago

Why do you think matter so varied

Natali [406]

Answer:

Matter is anything that has mass and takes up space. A mixture is matter that can vary in composition.....because, the substances in a heterogeneous mixture are not evenly mixed, two samples of the same mixture can have different amounts of the substance....

Hope this answer help u!!!!

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3 years ago

As a car comes to a skidding stop, what happens to the car’s energy

Vladimir79 [104]

The answer is 3. Internal energy decrease

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3 years ago

I need help with questions b and d, that’s all. Thank you.

Mkey [24]

b). The power depends on the RATE at which work is done.

Power = (Work or Energy) / (time)

So to calculate it, you have to know how much work is done AND how much time that takes.

In part (a), you calculated the amount of work it takes to lift the car from the ground to Point-A. But the question doesn't tell us anywhere how much time that takes. So there's NO WAY to calculate the power needed to do it.

The more power is used, the faster the car is lifted. The less power is used, the slower the car creeps up the first hill. If the people in the car have a lot of time to sit and wait, the car can be dragged from the ground up to Point-A with a very very very small power ... you could do it with a hamster on a treadmill. That would just take a long time, but it could be done if the power is small enough.

Without knowing the time, we can't calculate the power.

...

d). Kinetic energy = (1/2) · (mass) · (speed squared)

On the way up, the car stops when it reaches point-A.

On the way down, the car leaves point-A from "rest".

WHILE it's at point-A, it has no speed. So it has no (zero) kinetic energy.

7 0

2 years ago

Whenever two apollo astronauts were on the surface of the moon, a third astronaut orbited the moon. assume the orbit to be circu

almond37 [142]

Missing question:
"Determine (a) the astronaut’s orbital speed v and (b) the period of the orbit"

Solution

part a) The center of the orbit of the third astronaut is located at the center of the moon. This means that the radius of the orbit is the sum of the Moon's radius r0 and the altitude ( $h=430 km=4.3 \cdot 10^5 m$ ) of the orbit:
$r= r_0 + h=1.7 \cdot 10^6 m + 4.3 \cdot 10^5 m=2.13 \cdot 10^6 m$
This is a circular motion, where the centripetal acceleration is equal to the gravitational acceleration g at this altitude. The problem says that at this altitude, $g=1.08 m/s^2$ . So we can write
$g=a_c= \frac{v^2}{r}$
where $a_c$ is the centripetal acceleration and v is the speed of the astronaut. Re-arranging it we can find v:
$v= \sqrt{g r}= \sqrt{(1.08 m/s^2)(2.13 \cdot 10^6 m)}=1517 m/s = 1.52 km/s$

part b) The orbit has a circumference of $2 \pi r$ , and the astronaut is covering it at a speed equal to v. Therefore, the period of the orbit is
$T= \frac{2 \pi r}{v} = \frac{2\pi (2.13 \cdot 10^6 m)}{1517 m/s} =8818 s = 2.45 h$
So, the period of the orbit is 2.45 hours.

6 0

3 years ago