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3 years ago

Rachel travels 100km in 5hrs. Find her AVERAGE SPEED. i need work shown too

Physics

1 answer:

Brilliant_brown [7]3 years ago

4 0

Answer:

20kph

Explanation:

Since she travels 100kpm in 5 hours and 100 divided by 5 is 20 she would travel 20km in one hour

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You attach a 3.10 kg weight to a horizontal spring that is fixed at one end. You pull the weight until the spring is stretched b

dolphi86 [110]

Answer:

0.785 m/s

Explanation:

Hi!

To solve this problem we will use the equation of motion of the harmonic oscillator, i.e.

$x(t) = A cos(\omega t )+B sin(\omega t)$ - (1)

$\frac{dx}{dt}(t) = \omega (B cos(\omega t )- A sin(\omega t)$ - (1)

The problem say us that the spring is released from rest when the spring is stretched by 0.100 m, this condition is given as:

$x(0) = 0.100$

$\frac{dx}{dt}(0) = 0$

Since cos(0)=1 and sin(0) = 0:

$x(0)=A$

$\frac{dx}{dt}(0) = -B\omega$

We get

$A =0.100\\B = 0$

Now it say that after 0.4s the weigth reaches zero speed. This will happen when the sping shrinks by 0.100. This condition is written as:

$x(0.4) = - 0.100$

Since

$x(t) = 0.100 cos(\omega t)\\ -0.100=x(0.4)=0.100cos(\omega 0.4)$

This is the same as:

$-1 = cos(0.4\omega)$

We know that cosine equals to -1 when its argument is equal to:

(2n+1)π

With n an integer

The first time should happen when n=0

Therefore:

π = 0.4ω

ω = π/0.4 -- (2)

Now, the maximum speed will be reached when the potential energy is zero, i.e. when the sping is not stretched, that is when x = 0

With this info we will know at what time it happens:

$0 = x(t) = 0.100cos(\omega t)$

The first time that the cosine is equal to zero is when its argument is equal to π/2

i.e.

$t_{maxV}=\pi /(2\omega)$

And the velocity at that time is:

$\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\omega t_{maxV})\\\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\pi/2)\\$

But sin(π/2) = 1.

Therefore, using eq(2):

$\frac{dx}{dt}(t_{maxV} ) = 0.100*\omega = 0.100\frac{\pi}{0.400} = \pi/4$

And so:

$V_{max} = \pi / 4 =0.785$

6 0

2 years ago

What elements are in NaOH

agasfer [191]

Answer: Sodim hydroxide have a formula of NaOH . So the elements present in the compound is sodium,oxygen and hydrogen.

Explanation:

3 0

2 years ago

Read 2 more answers

The units we use to measure the sound intensity level are _____.

Sergio039 [100]

Answer:

decibels (dB)

Explanation:

The sound intensity level is a quantity derived from the sound intensity.

The intensity of a wave is defined as the power of the source of the wave divided by the area through which the power of the wave is spread, mathematically:

$I=\frac{P}{A}$

where

P is the power of the source

$A=4\pi r^2$ is the surface area over which the wave spreads (assuming that the wave propagates in all directions, it corresponds to the surface area of a sphere of radius $r$ , where r is the distance between the source of the wave and the observer)