A 60.0 kg ballet dancer stands on her toes during a performance with four square inches (26.0 cm2) in contact with the floor. What is the pressure exerted by the floor over the area of contact in the following cases?

(a) if the dancer is stationary
(b) if the dancer is leaping upwards with an acceleration of 5.00 m/s2

Respuesta :

Answer:

Explanation:

Given

Mass of dancer [tex]m=60\ kg[/tex]

Area of contact [tex]A=26\ cm^2[/tex]

(a)If dancer is stationary

Pressure exerted by Floor is given by load per unit area of contact

[tex]P=\frac{weight}{A}[/tex]

[tex]P=\frac{mg}{A}[/tex]

[tex]P=\frac{60\times 9.8}{26\times 10^{-4}}[/tex]

[tex]P=226.153 kN[/tex]

(b)If dancer is leaping upwards with an acceleration of [tex]a=5 m/s^2[/tex]

So apparent weight of dancer is [tex]W'=mg+ma[/tex]

[tex]W'=m(g+a)=60\cdot (9.8+5)[/tex]

[tex]W'=888\ N[/tex]

[tex]Pressure=\frac{W'}{A}[/tex]

[tex]Pressure=\frac{888}{26\times 10^{-4}}[/tex]

[tex]=341.53\ kN[/tex]      

The pressure exerted by the dancer on the floor when the dancer is stationary is 2.26 x 10⁵ N/m².

The pressure exerted by the dancer on the floor when the dancer is leaping up is 3.42 x 10⁵ N/m².

The given parameters;

  • mass of the dancer, m = 60 kg
  • area of her toe, A = 26 cm² = 26 x 10⁻⁴ m²

The pressure exerted by the dancer on the floor when the dancer is stationary is calculated as follows;

F = ma + mg

a = 0 (stationary)

F = mg

[tex]P = \frac{F}{A} = \frac{mg}{A} = \frac{60 \times 9.8}{26\times 10^{-4}} = 2.26\times 10^5 \ N/m^2[/tex]

The pressure exerted by the dancer on the floor when the dancer is leaping up is calculated as follows;

F = ma + mg

F = m(a + g)

[tex]P = \frac{m(a + g)}{A} = \frac{60(5 + 9.8)}{26\times 10^{-4}} = 3.42 \times 10^5 \ N/m^2[/tex]

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