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2 years ago

9

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1 answer:

Yanka [14]2 years ago

4 0

A. A stretched catapult can do work when released so it must have potential energy.

b. A stone on the ground will not move on its own ever again so it has zero energy.

c. In order to roll an object there must be a friction force between the object and the ground (otherwise it will slide)

d. To lift a stone you must overcome the weight which is the force due to gravity.

e. Work and energy are both measured in Joules.

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The half-life of a certain element is 100 days. How many half-lives will it be before only one-eighth of this element remains?

Natalka [10]

Answer:

3

Explanation:

The half-life is the time it takes for the amount of radioactive isotope to halve. Therefore, we have:

- After 1 half-life, only 1/2 of the element will be left

- After 2 half-lives, only 1/4 of the element will be left

- After 3 half-lives, only 1/8 of the element will be left

So, it will take 3 half-lives for the element to become 1/8 of its original amount.

Mathematically, this can be also verified by using the equation

$\frac{N(t)}{N_0}=(\frac{1}{2})^\frac{t}{\tau_{1/2}}$

where

N(t) is the amount of the element left at time t

N0 is the initial amount of the element

$\tau_{1/2}$ is the half-life

Substituting $t=3\tau_{1/2}$ (3 half-lives), we find

$\frac{N(t)}{N_0}=(\frac{1}{2})^3=\frac{1}{8}$

7 0

2 years ago

Find a unit vector normal to the plane containing Bold u equals 2 Bold i minus Bold j minus 3 Bold k and Bold v equals negative

Nastasia [14]

Answer:

$\hat{w}=\dfrac{\vec{5i+13j-k}}{13.92}$

Explanation:

It is given that,

$\vec{u}=2i-j-3k$

$\vec{v}=-3i+j-2k$

Taking the cross product of v and v such that,

$\vec{w}=u\times v$

$\vec{w}=(2i-j-3k)\times (-3i+j-2k)$

$\vec{w}=5i+13j-k$

$|w|=\sqrt{5^2+13^2(-1)^2}$

|w| = 13.92

Let $\hat{w}$ is the unit vector normal to the plane containing u and v. So,

$\hat{w}=\dfrac{\vec{w}}{|w|}$

$\hat{w}=\dfrac{\vec{5i+13j-k}}{13.92}$

Hence, this is the required solution.

7 0

3 years ago

Who was the first person to walk on the moon ?

liq [111]

Answer:

god correct correct

Explanation:

8 0

3 years ago

Read 2 more answers

The total length of the wire of potentiometer is 10m. A potential gradient of 0.0015 V/cm is obtained when a steady current is p

andreyandreev [35.5K]

Answer:

this picture might help you

Explanation:

if you think correct pls mark brainliest

3 0

2 years ago

I'm stuck on question 3. Could anyone please explain it?

sergiy2304 [10]

Peak voltage is 2
period is 40ms
frequency = 1/period = 25Hz

5 0

2 years ago