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$$
\begin{array}{c}{\text { Determine the mass and the weight of the air contained in a room }} \\ {\text { whose dimensions are } 6 \mathrm{m} \times 6 \mathrm{m} \times 6 \mathrm{m} \text { . } \mathrm{gm} \text { . }} \\ {\text { Assume the density of the air is } 1.16 \mathrm{kg} / \mathrm{m} 3}\end{array}
$$

$$
6 \times 6 \times 8 m
$$

$$
\rho=1.16 \mathrm{kg} / m^ 3
$$

$$
m=\rho V=1.16 *(6 \times 6 \times 8)=334.1 \mathrm{kg}
$$

$$
w=m g=334.1 * 9.81=3277 N
$$

$$
\begin{array}{c}{\text { A } 3 \text { -kg rock is thrown upward with a force of } 200 \mathrm{N} \text { at a location where }} \\ {\text { the local gravitational acceleration is } 9.79 \mathrm{m} / \mathrm{s} 2 .} \\ {\text { Determine the acceleration of the rock, in } \mathrm{m} / \mathrm{s} 2}\end{array}
$$

$$
F=m a
$$

$$
w=m g \quad=3 * 9.79=29.37 N
$$

$$
F_\text { net }=200-29.37=170.6 \mathrm{N}
$$

$$
\rho=\frac{F}{m}=\frac{170 \cdot 6}{3}=56.9 \mathrm{m/s}^{2}
$$

$$
\text { The constant-pressure specific heat of air at } 25^{\circ} \mathrm{C} \text { is } 1.005 \mathrm{kJ} / \mathrm{kg}^{\circ} \mathrm{C}.
$$

$$
\text { Express this value in } \mathrm{kJ} / \mathrm{kg}-\mathrm{K} \text { . }
$$$$
\mathrm{J} / \mathrm{g} ^{\circ} \mathrm{C}, \mathrm{kcal} / \mathrm{kg} {-}^{\circ} \mathrm{C}, \text { and } \mathrm{Btu} / \mathrm{Ibm} {-}^{\circ} \mathrm{F}.
$$

$$
1.005 \frac{\mathrm{k}_{\mathrm{J}}}{\mathrm{kg} \cdot \mathrm{c}^{\circ}}
$$

$$
C_{P}=\left(1.005 \frac{k_{J}}{k g \cdot c^{\circ}}\right)
$$$$
\left(\frac{\frac{1 k J}{k g \cdot k}}{\frac{1 k J}{k g \cdot c^{\circ}}}\right)
$$$$
=1.005 \mathrm{kg} / \mathrm{kg} \cdot \mathrm{k}
$$

$$
C_{P}=\left(1.005 \frac{k J}{k g \cdot c^{\circ}}\right)
$$$$
\left(\frac{1000}{1000}\right)=1.005 \ \mathrm{J} / g . \mathrm{c}^{\circ}
$$

$$
C_{P}=\left(1.005 \frac{k_J}{k g \cdot c^{\circ}}\right)
$$$$
\left(\frac{1 K cal}{4.1868 k J}\right)
$$$$
=0.24 \frac{\mathrm{k cal}}{\mathrm{kg} \cdot \mathrm{c}^{\circ}}
$$

 

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