Question

note: assume the specific heat capacity of water is 4186 j/kg°c and the specific heat capacity of soya bean oil is 1970 j/kg°c.

1. consider mixing 0.45 kg of water at 25°c to another 0.45 kg of water at 45°c. the final temperature of the mixture is

(a) 36°c
(b) 45°c
(c) 35°c
(d) 56°c
(e) none of the above
note: take the specific heat capacity of water as 4186 j/kg°c

1. what change in temperature will 7500 j of heat raise 5 kg of unknown pan. the specific heat of unknown pan is 236 j/kg°c

(a) 6.360°c
(b) 5.95 °c
(c) 23.86 °c
(d) 100.89°c
(e) none of the above

1. which of the following instrument can be used to measure the temperature of an object?

(a) thermistor
(b) thermometer
(c) speedometer
(d) barometer
(e) none of the above

Explanation:

Question 5

Step1: Set up heat transfer equation

Heat lost by hot water = Heat gained by cold water. Using \(Q = mc\Delta T\), \(m_1c(T_1 - T) = m_2c(T - T_2)\). Here \(m_1=m_2 = 0.45\space kg\), \(T_1 = 45^{\circ}C\), \(T_2=25^{\circ}C\) and \(c = 4186\space J/kg^{\circ}C\). The \(c\) and \(m\) terms cancel out.

Step2: Solve for \(T\)

\(45 - T=T - 25\). Add \(T\) to both sides: \(45=2T - 25\). Add 25 to both sides: \(70 = 2T\). Divide by 2: \(T=\frac{70}{2}=35^{\circ}C\)

Step1: Use heat - temperature change formula

The formula \(Q=mc\Delta T\) can be rearranged to \(\Delta T=\frac{Q}{mc}\). Given \(Q = 7500\space J\), \(m = 5\space kg\) and \(c=236\space J/kg^{\circ}C\)

Step2: Calculate \(\Delta T\)

\(\Delta T=\frac{7500}{5\times236}=\frac{7500}{1180}\approx6.36^{\circ}C\)

A thermistor is a type of resistor whose resistance varies significantly with temperature (used in temperature - sensing circuits). A thermometer is a device specifically designed to measure the temperature of an object or a substance. A speedometer measures the speed of a vehicle. A barometer measures atmospheric pressure.

Answer:

C. \(35^{\circ}C\)

Question 6