What is the main factor that influence how long a star burns

What type of interaction occurs when a wave hits an object that it cannot pass?

alexandr402 [8]

It makes an echo and it circles around it.

5 0

3 years ago

Suppose a police officer is 1/2 mile south of an intersection, driving north towards the intersection at 40 mph. At the same tim

blagie [28]

Answer:

75.36 mph

Explanation:

The distance between the other car and the intersection is,

$x=x_{0}+V t \\ x=\frac{1}{2}+V t$

The distance between the police car and the intersection is,

$y=y_{0}+V t$

$y=\frac{1}{2}-40 t$

(Negative sign indicates that he is moving towards the intersection)

Therefore the distance between them is given by,

$z^{2}=x^{2}+y^{2}(\text { Using Phythogorous theorem })$

$z^{2}=\left(\frac{1}{2}+V t\right)^{2}+\left(\frac{1}{2}-40 t\right)^{2} \ldots \ldots \ldots(1)$

The rate of change is,

$2 z \frac{d z}{d t}=2\left(\frac{1}{2}+V t\right) V+2\left(\frac{1}{2}-40 t\right)(-40)$

$2 z \frac{d z}{d t}=V+2 V^{2} t-40+3200 t \ldots \ldots \ldots$

Now finding $z$ when $t=0,$ from (1) we have

$z^{2}=\left(\frac{1}{2}+V(0)\right)^{2}+\left(\frac{1}{2}-40(0)\right)^{2}$

$z^{2}=\frac{1}{4}+\frac{1}{4}=\frac{1}{2} \\ z=\sqrt{\frac{1}{2}} \approx 0.7071$

The officer's radar gun indicates 25 mph pointed at the other car then, $\frac{d z}{d t}=25$ when $t=0,$ from

From (2) we get

$2(0.7071)(25)=V+2 V^{2}(0)-40+3200(0)$

$2(0.7071)(25)=V+2 V^{2}(0)-40$

$35.36=V-40$

$V=35.36+40=75.36$

Hence the speed of the car is $75.36 mph$

7 0

3 years ago

If the half-life of niobium-91 is 680 years, how long will it take for the decay described in the previous question?

Svet_ta [14]

2040

15.4+2.2/2 until it equals 2.2
( divide by 3)

680(years)*3 devisions = 2040

3 0

4 years ago

Read 2 more answers

You drop a batitin a stationary elevator and the ball hits the floor in o 50 s. How long does it take for the ball to hit the fl

solmaris [256]

Answer:

option (a) 0.61 s

Explanation:

Given;

Time taken by the ball to reach the ground = 0.50 s

Let us first calculate the distance through which the ball falls on the ground

from the Newton's equation of motion, we have

$s=ut+\frac{1}{2}at^2$

where,

s is the distance

a is the acceleration

t is the time

here it is the case of free fall

thus, a = g = acceleration due to gravity

u = initial speed of the ball = 0

on substituting the values, we get

$s=0\times 0.50+\frac{1}{2}\times9.8\times0.50^2$

or

s = 1.225 m

Now,

when the elevator is moving up with speed of 1.0 m/s

the initial speed of the ball = -1.0 m/s (as the elevator is moving in upward direction)

thus , we have

$s=ut+\frac{1}{2}at^2$

or

$1.225=-1.0\times\ t+\frac{1}{2}\times9.8t^2$

or

4.9t^2 - t - 1.225 = 0

or

t = 0.612 s

hence, the correct answer is option (a) 0.61 s

4 0

4 years ago

A _______ satellite records reflected wavelengths from Earth's surface.

Oksana_A [137]

<span>It is LandSat, a NASA based satelite that records, on a daily basis, multiple reflected wavelengths from the Earth's surface. The satelite measures reflection from both land and ocean upon the Earth. The system is utilised by scientists an policy makers around the world. </span>

3 0

3 years ago

Read 2 more answers