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2 years ago

11

A century ago, swords were made from various metals, especially steel. The property that makes steel a good choice for sword mak

ing is _____.

2 answers:

8_murik_8 [283]2 years ago

8 0

Hardness and strength

andreev551 [17]2 years ago

3 0

<em>The answer to this question is strength</em>

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Which statements describe vectors?

laila [671]

Answer:

Vectors have a size and direction. Each of the existing vector quantity has a magnitude and a direction. Having direction along with the magnitude is the difference of a vector quantity from a scalar quantity. Vectors are indicates with arrows.

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1 year ago

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if a car is moving on a highway at 70 kilometers per hour going east, what happens to its speed and velocity

Andrej [43]

The speed is constant since there is no opposite force facing the car

That’s my best guest hope it helps !! :)

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2 years ago

A dog running to the right at 4 m/s sees a ball and accelerates steadily to catch it. The dog accelerates to the right at a rate

antoniya [11.8K]

Answer:

D.-4.798m/s

Explanation:

Greetings !

Given values

$u= 4ms \\ a = 0.21ms {}^{2} \\ t = 3.8sec$

Solve for V of the given expression

Firstly, recall the velocity-time equation

$v = u + at$

plug in known values to the equation

$v = (4) + (0.21)(3.8)$

solve for final velocity

$v = 4.792ms$

Hope it helps!

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1 year ago

Recall from Chapter 1 that a watt is a unit of en- ergy per unit time, and one watt (W) is equal to one joule per second ( J·s–1

harkovskaia [24]

Answer:

Explanation:

The energy of a photon is given by the equation $E_p=h f$ , where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of $E_N=N h f$ .

We also know that frequency and wavelength are related by $f=\frac{c}{\lambda}$ , so we have $E_N=\frac{N h c}{\lambda}$ , where c is the <em>speed of light</em>.

We will want the number of photons, so we can write

$N=\frac{\lambda E_N}{h c}$

We need to know then how much energy do we have to calculate N. The equation of power is $P=E/t$ , so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be $E_N$ .

Putting this paragraph in equations:

$E_N=(\frac{4}{100})E=0.04Pt=(0.04)(100W)(1s)=4J$ .

And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:

$N=\frac{\lambda E_N}{h c}=\frac{(520 \times10^{-9}m) (4J)}{(6.626\times10^{-34}Js) (299792458m/s)}=1.047 \times10^{19}$

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2 years ago

Ryan is driving home from work and notices a deer leaping onto the road about 25 m in front of his car. He immediately applies t

Anvisha [2.4K]

Answer:

mu = 0.56

Explanation:

The friction force is calculated by taking into account the deceleration of the car in 25m. This can be calculated by using the following formula:

$v^2=v_0^2+2ax\\$

v: final speed = 0m/s (the car stops)

v_o: initial speed in the interval of interest = 60km/h

= 60(1000m)/(3600s) = 16.66m/s

x: distance = 25m

BY doing a the subject of the formula and replace the values of v, v_o and x you obtain:

$a=\frac{v^2-v_o^2}{2x}=\frac{0m^2/s^2-(16.66m/s)^2}{2(25m)}=-5.55\frac{m}{s^2}$

with this value of a you calculate the friction force that makes this deceleration over the car. By using the Newton second's Law you obtain:

$F_f=ma=(1490kg)(5.55m/s^2)=8271.15N$

Furthermore, you use the relation between the friction force and the friction coefficient:

$F_f= \mu N=\mu mg\\\\\mu=\frac{F_f}{mg}=\frac{8271.15N}{(1490kg)(9.8m/s^2)}=0.56$

hence, the friction coefficient is 0.56

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2 years ago