Question

Para comenzar a caminar horizontalmente, una persona debe acelerar su cuerpo hacia adelante haciendo uso del rozamiento estático. Una persona puede alcanzar típicamente una velocidad de 2.0 m/s en una distancia de 30 cm, partiendo del reposo. Suponiendo una aceleración constante, a) dibuje un diagrama de fuerzas para el inicio del paseo. (b) Aplique la segunda de ley de Newton para hallar el coeficiente de rozamiento estático mínimo para el paseo descrito. (c) Si se desea caminar más rápido, ¿haría falta más o menos rozamiento? ¿Por qué? (d) Suponga que el suelo es resbaladizo y que el coeficiente de rozamiento es menor que el calculado anteriormente. Explique por qué sigue siendo posible caminar, pero el paseo será mucho más cansado.

To start walking horizontally, a person must accelerate their body towards
forward making use of static friction. A person can typically achieve a
speed of 2.0 m / s in a distance of 30 cm, starting from rest. Assuming an acceleration
constant, a) draw a force diagram for the start of the walk. (b) Apply the second law
of Newton to find the minimum static coefficient of friction for the ride described. (c)
If you want to walk faster, would you need more or less friction? Why? (d) Suppose that the
The floor is slippery and the coefficient of friction is less than that calculated previously.
Explain why it is still possible to walk, but the walk will be much more tiring.

Answer 1

(a)

(b)  We have,

  

Where, v is final velocity

u is initial velocity

a is acceleration

s is distance

Given, v = 2.0 m/s, u = 0 m/s, s = 30 cm = 0.3 m

So,   

or,

or,   

Now from Newton's second law of motion,

  F = ma

Force of static friction =    (g is acceleration due to gravity)

So,  

  

or,  

or,  

(c)

If you want to walk faster, you need more friction. If you walk faster you will need to apply more backward force on ground as a result more friction will act.

(d)

If friction is less, you can't apply much backward force on ground before your foot starts to slip. it means surface can't apply much forward force on you. Hence the walk will be much tiring.