Question 4 of 10

Why are all machines not 100% efficient A. Mass B. Gravity C. Friction D. Distance

Anon25 [30]

All machines are not 100% efficient because of C. Friction

7 0

3 years ago

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Which of the following is an ionic compound ? A. Gold

quester [9]

Among the given choices, the ionic compound is D. Magnesium Chloride (MgCl2) where magnesium has a +2 charge while chloride has a -1 charge. Ionic compounds are chemical compounds comprising of ions held together by electrostatic forces named as ionic bonding.

7 0

2 years ago

What is the sprinters output at 2.0 s, 4.0 s and 6.0 s?

kari74 [83]

A 59 kg sprinter, starting from rest, runs 47 m in 7.0 s at constant acceleration.?

What is the sprinter's power output at 2.0 s, 4.0 s, and 6.0 s?

Instantaneous Power is the force times velocity

P = Fv

Because the acceleration is constant, the force will be constant as well

F = ma

P = mav

for constant acceleration, the velocity at each time is found using

v = at

P = ma(at) = ma²t

find the acceleration using kinematic equation

s = ½at²

a = 2s/t²

a = 2(47) / 7.0²

a = 1.918 m/s²

P(2.0) = 59(1.918²)2.0 = 434.25 W = 0.43 kW

P(4.0) = 59(1.918²)4.0 = 868.51 W = 0.87 kW

P(6.0) = 59(1.918²)6.0 = 1302.76 W = 1.3 kW

I hope this helped.

5 0

3 years ago

Which statement is a hypothesis?

shusha [124]

I believe the answer should be D

8 0

2 years ago

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The Sun’s surface temperature is about 5800 K and its spectrum peaks at 5000 Å. An O-type star’s surface temperature may be 40,0

nirvana33 [79]

(a) $7.25\cdot 10^{-8}m$

Wien's displacement law is summarized by the equation

$\lambda = \frac{b}{T}$

where

$\lambda$ is the peak wavelength

$b=2.898\cdot 10^{-3} m \cdot K$ is Wien's displacement constant

T is the absolute temperature at the surface of the star

For an O-type star, we have

T = 40,000 K

Therefore, its peak wavelength is

$\lambda = \frac{2.898\cdot 10^{-3}}{40000}=7.25\cdot 10^{-8}m$

(b) Ultraviolet

We can answer this part by looking at the wavelength range of the different parts of the electromagnetic spectrum:

gamma rays

X-rays 1 nm - 1 pm

ultraviolet 380 nm - 1 nm

visible light 750 nm - 380 nm

infrared $25 \mu m - 750 nm$

microwaves 1 mm - $25 \mu m$

radio waves > 1 mm

The peak wavelength of this star is

$\lambda=7.25\cdot 10^{-8}m=72.5 nm$

Therefore, it falls in the ultraviolet region.

(c) No

The Keck telescopes is actually a system of 2 telescopes in the Keck Observatory, located in Mauna kea, Hawai.

The two telescopes, thanks to several instruments, are able to detect much of the electromagnetic radiation in the visible ligth and infrared parts of the spectrum. However, they are not able to detect light in the ultraviolet region: therefore, they cannot observe the star mentioned in the previous part of the problem.

7 0

3 years ago