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Deffense [45]
3 years ago
12

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. Wh

at 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
Physics
1 answer:
Anit [1.1K]3 years ago
5 0

Answer:

Explanation:

Given

Mass of dancer m=60\ kg

Area of contact A=26\ cm^2

(a)If dancer is stationary

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

P=\frac{weight}{A}

P=\frac{mg}{A}

P=\frac{60\times 9.8}{26\times 10^{-4}}

P=226.153 kN

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

So apparent weight of dancer is W'=mg+ma

W'=m(g+a)=60\cdot (9.8+5)

W'=888\ N

Pressure=\frac{W'}{A}

Pressure=\frac{888}{26\times 10^{-4}}

=341.53\ kN      

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2.5m/s

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          Acceleration = \frac{Final velocity - Initial velocity}{time}

  From the equation above, the unknown is final velocity:

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The plates of a parallel-plate capacitor are 2.50 mm apart, and each carries a charge of magnitude 77.0 nC. The plates are in va
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Answer:

Part A: 7500 V

Part B: 2.899×10⁻³ m²

Part C: 10.27 pF or 10.27×10⁻¹² F

Explanation:

Part A:

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E = V/d................ Equation 1

Where E = electric field intensity between the plates, V = potential difference between the plates, d = distance of separation between the plates

make V the subject of the equation above,

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Substitute into equation 2

V =  3.0×10⁶ (2.5×10⁻³ )

V = 7.5×10³ V

V = 7500 V

Part B:

Using,

E = Q/(e₀A).................... Equation 3

Where Q = Charge on each plate of the capacitor, A = Area of each plate, e₀ = constant = dielectric = permitivity of free space

make A the subject of the equation,

A = Q/(e₀E).............. Equation 4

Given: Q = 77 nC = 77×10⁻⁹ C, E = 3.0×10⁶ V/m

Constant: e₀ = 8.854×10⁻¹² F/m

Substitute into equation 4

A = 77×10⁻⁹/(8.854×10⁻¹²× 3.0×10⁶)

A = 77×10⁻⁹/(26.562×10⁻⁶)

A = 2.899×10⁻³ m²

A = 2.899×10⁻³ m².

Part C:

Using,

Q = CV.................. Equation 5

Where C = Capacitance of the capacitor

make C the subject of the equation

C = Q/V.............. Equation 6

Given: Q = 77 nC = 77×10⁻⁹ C, V = 7500 V

Substitute into equation 6

C = 77×10⁻⁹/7500

C = 10.27×10⁻¹² F

C = 10.27 pF

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