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Schach [20]
3 years ago
7

A21.0-kg block is initially at rest on a horizontal surface. A horizontal force of73.0N is required to set the block in motion,

after which a horizontal force of58.0N is required to keep the block moving with constant speed.(a) Find the coefficient of static friction between the block and the surface.(b) Find the coefficient of kinetic friction between the block and the surface.
Physics
1 answer:
Elanso [62]3 years ago
5 0

Answer:

a) μs=0.34

b) μk=0.27

Explanation:

Given that

Mass , m = 21 kg

Force required to move the block ,F= 73 N

The force required to keep the block in motion ,F ' = 58 N

Coefficient of the static friction  :

The maximum value of the static friction force

fr= μs m g

At rest position

F=  fr

73 = μs x 21 x 10   (take g= 10 m/s²)

\mu_s=\dfrac{73}{210}

μs=0.34

Therefore the Coefficient of the static friction  will be 0.34.

Coefficient of the kinetic  friction  ;

Value of the kinetic friction force   ,fr= μk m g

F' = Fr

To move the block at constant speed

58 = μs x 21 x 10                 (take g= 10 m/s²)

\mu_k=\dfrac{58}{210}

μk=0.27

Therefore the Coefficient of the static friction  will be 0.27.

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Lyrx [107]

This question is incomplete, the complete question is;

- Calculate the difference in blood pressure between the feet and top of the head of a person who is 1.80m Tall

- Consider a cylindrical segment of a blood vessel 2.70 cm long and 3.10 mm in diameter. What additional outward force would such a vessel need to withstand in the person's feet compared to a similar vessel in her head

Answer:

- the difference in blood pressure is 18698.4 Pa

- the additional outward force F is 4.86 N

Explanation:

Given the data in the question;

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now we substitute

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therefore the difference in blood pressure is 18698.4 Pa

Also given that;

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radius r = 3.10 mm / 2 = 1.55 mm = 0.00155 m

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we substitute

F = 18698.4 Pa × 2.6 × 10⁻⁴ m²

F = 4.86 N

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