The most important barriers to diffusion today are physical features of Earth's surface.

Physics

1 answer:

nikdorinn [45]3 years ago

7 0

Answer:

False

Explanation:

Physical features of earth's surface like mountains, deserts and oceans are not the barriers in today's modern world. Technological improvements in the transportation and communication has removed these barriers. So they are not barriers anymore.

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A man is standing on a platform that is connected to a pulley arrangement, as the drawing shows. By pulling upward on the rope w

leonid [27]

Answer:

The pulling force that the man should apply to create an upward acceleration of $1.20m/s^{2}$ is $P=621.5N$

Explanation:

As it shows in the drawing at the end, we have that the total mass of the man plus the platform is $113 kg$ , then the force downward $W$ is $W=mg=113Kg*9.8m/s^{2}=1107.4N$ .

Due the man needs to do a pulling force upward capable of lifting himself and the platform with an acceleration of $1.20m/s^{2}$ , this force should create an acceleration greater than gravity by $1.20m/s^{2}$ . then $a_{up}=g+1.2m/s^{2}=9.8m/s^{2}+1.2m/s^{2}=11m/s^{2}$ . Therefore the force should be $P_{up}=ma_{up}=113kg*11m/s^{2}=1243N$ .

Finally, as we have a pulley arrangement connected to the platform, it gives the man a mechanical advantage, so he has to do only half of that upward force

, therefore $P=\frac{1243N}{2}=621.5N$ .