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prohojiy [21]
2 years ago
7

A cave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. The lift i

s performed in three stages, each requiring a vertical distance of 12.0 m: (a) the initially stationary spelunker is accelerated to a speed of 2.90 m/s; (b) he is then lifted at the constant speed of 2.90 m/s; (c) finally he is decelerated to zero speed. How much work is done on the 77.0 kg rescue by the force lifting him during each stage
Physics
1 answer:
Leya [2.2K]2 years ago
5 0

Answer:

a) 323.4J

b) 0J

c) -323.4J

Explanation:

a) W=Fd

F=ma

solve for acc. using kinematics

v^2=vo^2+2a(x)

8.41=2a(12)

4.205=a(12)

0.35=a

F=(77)(0.35)

F=26.95N

W=26.95*12...... W=323.4J

b) No acceleration, thus no force, thus no work!

c) W=Fd

F=ma

find acc. using kinematics: v^2=vo^2+2a(x)

0=(2.9^2)+2a(12)

0=8.41+2a(12)

-8.41=2a(12)

-4.205=a(12)

-0.35=a

F=(77)(-0.35)

F=-26.95N

W=(-26.95)(12)

W=-323.4J

Yes, work can be negative!

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Answer:

an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of miles, and adapt to the characteristics of the surface below them. They are classified according to latitude and their continental or maritime source regions. Colder air masses are termed polar or arctic, while warmer air masses are deemed tropical. Continental and superior air masses are dry while maritime and monsoon air masses are moist. Weather fronts separate air masses with different density (temperature and/or moisture) characteristics. Once an air mass moves away from its source region, underlying vegetation and water bodies can quickly modify its character.When winds move air masses, they carry their weather conditions (heat or cold, dry or moist) from the source region to a new region. When the air mass reaches a new region, it might clash with another air mass that has a different temperature and humidity. This can create a severe storm.

Air masses can affect the weather because of different air masses that are different in temperature, density, and moisture. When two different air masses meet a front forms. This is one way air masses effect our weather.

5 0
3 years ago
I WILL MARK U BRAINLIEST IF U ANSWER THIS QUESTION! NEED IT ASAP PLS
Anuta_ua [19.1K]
  1. One common use of a convex mirror is as shaving mirror.
  2. One common use of convex mirror is as rear-view mirrors in automobiles vehicles.

<h3>What is a concave mirror?</h3>

A concave mirror is also referred to as a converging mirror and it can be defined as a type of mirror that is designed and developed with a reflective surface that is typically curved inward and away from the source of light.

Basically, one common use of a convex mirror include the following:

  • Shaving mirrors
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<h3>What is a convex mirror?</h3>

A convex mirror is also referred to as a diverging mirror and it can be defined as a type of mirror that is designed and developed with a reflective surface that typically bulges outward toward the source of light.

Basically, one common use of convex mirror is as rear-view mirrors in automobiles vehicles.

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8 0
1 year ago
A 25kg chair initially at rest on a horizontal floor requires 165 N force to set it in motion. Once the chair is in motion, a 12
bazaltina [42]

The coefficient of static friction between the chair and the floor is 0.67

Explanation:

Given:

Weight of the chair = 25kg

Force = 165 N (F_applied)

Force = 127 N (F_max)

To find: Coefficient of static friction  

The “coefficient of static friction” between a chair and the floor is defined as the ration of maximum force to the normal force acting on the chair  

μ_s=F_{max}/F_{n}  

The F_n is equal to the weight multiplied by its gravity

∴F_{n}=mg  

Thus the coefficient of static friction changes as

μ_s=F_{max}/mg

μ_{s} = =165N/((25kg)\times(9.80 m/s^2 ) )

= 0.67

3 0
2 years ago
A gun shoots a bullet with a velocity of 500 m/s. The gun is aimed horizontally and fired from a height of 1.5 m. How far does t
MrMuchimi

The bullet travels a horizontal distance of 276.5 m

The bullet is shot forward with a horizontal velocity u_x. It takes a time <em>t</em> to fall a vertical distance <em>y</em> and at the same time travels a horizontal distance <em>x. </em>

The bullet's horizontal velocity remains constant since no force acts on the bullet in the horizontal direction.

The initial velocity of the bullet has no component in the vertical direction. As it falls through the vertical distance, it is accelerated due to the force of gravity.

Calculate the time taken for the bullet to fall through a vertical distance <em>y </em>using the equation,

y=u_yt+\frac{1}{2} gt^2

Substitute 0 m/s for u_y, 9.81 m/s²for <em>g</em> and 1.5 m for <em>y</em>.

y=u_yt+\frac{1}{2} gt^2\\ 1.5 m=(0m/s)t+\frac{1}{2} (9.81m/s^2)t^2\\ t=\sqrt{\frac{2(1.5m)}{9.81m/s^2} } =0.5530s

The horizontal distance traveled by the bullet is given by,

x=u_xt

Substitute 500 m/s for u_x and 0.5530s for t.

x=u_xt\\ =(500m/s)(0.5530s)\\ =276.5m

The bullet travels a distance of 276.5 m.


5 0
3 years ago
Fiora starts riding her bike at 18 mi/h. After a while, she slows down to 12 mi/h, and maintains that speed for the rest of the
lord [1]

Answer:

t = 2.5 hours

Explanation:

given,

speed of the bike for t time= 18 mi/h

final speed of the bike after t time = 12 mi/h

total distance, D = 69 miles

total time, T= 4.5 hour

time for which speed of the bike is 18 mi/h = ?

we know distance = speed x time

now,

18 x t + 12 (4.5 - t) = 69

6 t + 54 = 69

6 t = 15

t = 2.5 hours

The bike was at the speed of 18 mi/h for 2.5 hours.

4 0
3 years ago
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