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ElenaW [278]
2 years ago
15

A dockworker loading crates on a ship finds that a 25-kg crate, initially at rest on a horizontal surface, requires a 72-N horiz

ontal force to set it in motion. However, after the crate is in motion, a horizontal force of 55 N is required to keep it moving with a constant speed. Find the coefficients of static and kinetic friction between crate and floor.
Physics
1 answer:
Gnom [1K]2 years ago
7 0

Answer:

Explanation:

Force of static friction = μs x mg

Given force of static friction = 72 N

μs x mg = 72

μs = 72 / mg

= 72 / 25 x 9.8

= .294

Force of kinetic  friction = μk x mg

Given force of kinetic  friction = 55

μk x mg = 55

μk = 55 / mg

= 55 / 25 x 9.8

= .2245

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Which prediction of weather is the most accurate for the next two days if there is an occluded front over the area?
alisha [4.7K]

The most accurate weather for the next two days would be dry warm weather or severe thunderstorms if there is an occluded front over the area.

<u>Explanation:</u>

The weather front that is created during the cyclogenesis process is an occluded front in meteorology. Cyclogenesis process is the development of extra-tropical cyclone and its intensification.

During the occurrence of this, the warm air is occluded (separated) from the center of cyclone at the surface of the earth.

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3 years ago
A helicopter lifts a 72 kg astronaut 15 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/
NemiM [27]

Answer:

a) F_H=776.952\ N

b) F_g=706.32\ N

c) v=5.4249\ m.s^{-1}

d) KE=1059.48\ J

Explanation:

Given:

  • mass of the astronaut, m=72\ kg
  • vertical displacement of the astronaut, h=15\ m
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a)

<u>Now the force of lift by the helicopter:</u>

Here the lift force is the resultant of the force of gravity being overcome by the force of helicopter.

F_H-F_g=m.a

where:

  • F_H= force by the helicopter
  • F_g= force of gravity

F_H=72\times 0.981+72\times9.81

F_H=776.952\ N

b)

The gravitational force on the astronaut:

F_g=m.g

F_g=72\times 9.81

F_g=706.32\ N

d)

Since the astronaut has been picked from an ocean we assume her initial velocity to be zero, u=0\ m.s^{-1}

using equation of motion:

v^2=u^2+2a.h

v^2=0^2+2\times 0.981\times 15

v=5.4249\ m.s^{-1}

c)

Hence the kinetic energy:

KE=\frac{1}{2} m.v^2

KE=0.5\times 72\times 5.4249^2

KE=1059.48\ J

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