Question

Determine the appropriate coefficient of friction in each case. show all you solutions.

1.It takes 59 N of horizontal force to get a 22 kg leather suitcase just starting to move across a floor. find us (hint fn=fg=mg)

2. A horizontal force of 54 N keeps the suitcase in moving at a constant velocity. find uk (hint fn=fg=mg)

Answer 1

Answer on Question #45620 – Physics, Mechanics | Kinematics | Dynamics

Determine the appropriate coefficient of friction in each case. show all you solutions.

1. It takes $59\,N$ of horizontal force to get a $22\,kg$ leather suitcase just starting to move across a floor. find us (hint $fn=fg=mg$)

2. A horizontal force of $54\,N$ keeps the suitcase in moving at a constant velocity. find uk (hint $fn=fg=mg$)

By the definition of friction:

$$F = \mu N$$

Where $\mu$ – is a coefficient of friction, $N$ – normal force.

From this equation we can find coefficient of friction:

$$\mu = \frac{F}{N}$$

On a horizontal plane, normal force will be equal to the weight of the body.

$$\mu = \frac{F}{mg}$$

1. In the first case we have static friction, so coefficient of static friction:

$$\mu_{st} = \frac{F_{st}}{mg}$$ $$\mu_{st} = \frac{59\,N}{22\,kg \cdot 9.8\, \frac{m}{s^2}} \approx 0.27$$

2. When suitcase is moving with constant velocity, we will get kinetic friction:

$$\mu_{k} = \frac{F_{k}}{mg}$$ $$\mu_{k} = \frac{54\,N}{22\,kg \cdot 9.8\, \frac{m}{s^2}} \approx 0.25$$

Answer: Coefficients of friction are:

- static friction $\mu_{st} \approx 0.27$

- kinetic friction $\mu_{k} \approx 0.25$

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