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3 years ago

50 J of work was performed in 20 seconds. How much power was used to perform this task? A. 0.4 W B. 2.5 W C. 4 W D. 24.5 W

Physics

1 answer:

Ugo [173]3 years ago

5 0

Answer:

B. 2.5 W

Explanation:

Power: This can be defined as the rate at which energy used or it i the rate at which work is done. The S.I unit of power is Watt (W).

Mathematically,

Power = Energy or work/Time

P = W/t ........................Equation 1

Where P = power used to perform the task, W = work, t = time.

Given: W = 50 J, t = 20 s.

Substitute into equation 1

P = 50/20

P = 2.5 W.

Hence the power is 2.5 W.

The right option is B. 2.5 W

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Answer:

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Explanation:

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A bicycle tire has a pressure of 7.00×105 N/m2 at a temperature of 18.0ºC and contains 2.00 L of gas. What will its pressure be

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Answer:

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Explanation:

from the ideal gas law we have

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$\rho = \frac{7.00 10^{5}}{287(18+273)}$

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for m_2

$m_2 = \rho V_i - V_removed$

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WE KNOW

PV = mRT

V, R and T are constant therefore we have

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$\frac{p_2}{p_1}=\frac{m_2}{m_1}$

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A student team is to design a human powered submarine for a design competition. The overall length of the prototype submarine is

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Answer:

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b) The drag force is 10.32 N

Explanation:

a) The Reynold´s number for the model and prototype is:

$Re_{m} =\frac{p_{m}V_{m}L_{m} }{u_{m} }$

$Re_{p} =\frac{p_{p}V_{p}L_{p} }{u_{p} }$

Equaling both Reynold's number:

$\frac{p_{p}V_{p}L_{p} }{u_{p} }=\frac{p_{m}V_{m}L_{m} }{u_{m} }$

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b) The drag force is:

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