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Vladimir [108]
3 years ago
5

PLEASE PLEASE HELP! this is on newton’s 2nd law! i will award 20 points and make you brainliest! ASAP PLEASE! ;)

Physics
2 answers:
horsena [70]3 years ago
5 0

Answer: The correct answer is B

Explanation: The string is pulling right and the string is unraveling causing it to accelerate left

Elenna [48]3 years ago
3 0

Answer:

b

Explanation:

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A stationary police car emits a sound of frequency 1240 HzHz that bounces off of a car on the highway and returns with a frequen
Tju [1.3M]

Answer

given,

frequency from Police car= 1240 Hz

frequency of sound after return  = 1275 Hz

Calculating the speed of the car = ?

Using Doppler's effect formula

Frequency received by the other car

  f_1 = \dfrac{f_0(u + v)}{u}..........(1)

u is the speed of sound = 340 m/s

v is the speed of the car

Frequency of the police car received

  f_2= \dfrac{f_1(u)}{u-v}

now, inserting the value of equation (1)

  f_2= f_0\dfrac{u+v}{u-v}

  1275=1240\times \dfrac{340+v}{340-v}

  1.02822(340 - v) = 340 + v

   2.02822 v = 340 x 0.028822

   2.02822 v = 9.799

   v = 4.83 m/s

hence, the speed of the car is equal to v = 4.83 m/s

5 0
3 years ago
A central air conditioner in a typical American home operates on a 220-V circuit and draws about 15 A
Zepler [3.9K]

Answer:

Find answers below.

Explanation:

Given the following data;

Voltage = 220V

Current = 15 A

a. To find the power;

Power = current * voltage

Power = 15 * 220

Power = 3300 Watts

b. To find the energy;

Time = 8 hours = 60 * 60 * 8 = 28800 seconds

Energy = power * time

Energy = 3300 * 8

Energy = 26400

Energy = 26.4 Kwh

c. Cost = 13 cents

Cost = 13 * 31 * 26.4

Cost = 106392 cents

8 0
2 years ago
If you start a new school year by changing bad habits from last school year and your grades improve which approach would this be
Ivanshal [37]

Answer:

Evolutionary

Explanation:

8 0
3 years ago
What can you conclude about plastic and copper from the observations given above?
ipn [44]
What are the "observations above" in this question?
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3 years ago
(b) A ball is thrown from a point 1.50 m above the ground. The initial velocity is 19.5 m/s at
Nataly_w [17]

The answers are:

(i) 6.35m

(ii) 20.2 m/s


It seems like you already have the answer, but let me show you how to get it:


You have two givens:

Vi = 19.5m/s

Θ = 30°

dy = 1.50m (This is not the maximum height, just to be clear)


When working with these types of equations, you just need to know your kinematics equations. For projectiles launched at an angle, you will need to first break down the initial velocity (Vi) into its horizontal (x) and vertical (y) components.


*<em>Now remember this, if you are solving for something in the horizontal movement always use only x-components. When solving for vertical movements, always use y-components. </em>


Let's move on to breaking down the initial velocity into both y and x components.


Viy = SinΘVi = (Sin30°)(19.5m/s) = <em>9.75 m/s</em>

Vix = CosΘVi = (Cos30°)(19.5m/s) = <em>16.89 m/s</em>


Okay, so we have that down now. The next step is to decide which kinematics equation you will use. Because you have no time, you need to use the kinematic equation that is not time dependent.


(i) Maximum height above the ground


Remember that the object was thrown 1.50m above the ground. So we save that for later. First we need to solve for the maximum height above the horizontal, or the point where it was thrown.


The kinematics equation you will use is:

Vf^{2} = Vi^{2}+2ad


Where:

Vf = final velocity

Vi = inital velocity

a = 9.8m/s²

d = displacement


We will derive our displacement from this equation. And you will come up with this:

d = \dfrac{Vf^{2}-Vi^{2}}{2a}


Again, remember that we are looking for a vertical component or y-component because we are looking for HEIGHT. So we use this plugging in vertical values only.


Vf at maximum height is always 0m/s because at maximum height, objects stop. Also because gravity is a downwards force you will use -9.8m/s².

Vfy = 0 m/s a = -9.8m/s² Viy = 9.75m/s

dy = \dfrac{Vfy^{2}-Viy^{2}}{2a}

dy = \dfrac{0^{2}-(9.75m/s)^{2}}{2(-9.8m/s^{2})}

dy = \dfrac{0^{2}-(9.75m/s)^{2}}{2(-9.8m/s^{2})}

dy = \dfrac{-95.0625m^{2}/s^{2}}{-19.6m/s^{2}}

dy = 4.85m


So from the point it was thrown, it reached a height of 4.85m. Now we add that to the height it was thrown to get the MAXIMUM HEIGHT <em>ABOVE THE GROUND.</em>


4.85m + 1.50m = 6.35m


(ii) Speed before it strikes the ground. (Vf=resultant velocity)

Okay, so here we need to consider a couple of things. To get the VF we need to first figure out the final velocities of both the x and y components. We are combining them to get the resultant velocity.


Vfx = horizontal velocity = Initial horizontal velocity (Vix). This is because gravity is not acting upon the horizontal movement so it remains constant.


Vfy = ?

VF =?


We need to solve this, again, using the same formula, but this time, you need to consider we are moving downwards now. So this time, instead of Vfy being 0 m/s, Viy is now 0 m/s. This is because it started moving from rest.


Vfy^{2} = Viy^{2}+2ad

Vfy^{2} = 0m/s^{2}+2(9.8m/s^{2}(6.35m)

\sqrt{Vfy^{2}} = \sqrt{124.46m^{2}/s^{2}}

Vfy= 11.16m/s


OKAY! We are at our last step. Now to get the resultant velocity, we apply the Pythagorean theorem.


Vf^{2} = Vfx^{2} + Vfy^{2}

\sqrt{Vf^{2}} = \sqrt{(16.89m/s)^{2}+(11.16m/s)^{2}}

Vf =20.2m/s


The ball was falling at 20.2m/s before it hit the ground.

8 0
3 years ago
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