15. The driver of a minibus which is moving at \( 80 \mathrm{~km} / \mathrm{h} \) notices a road block a short distance ahead. He applies brakes immediately so that the minibus moves with a constant deceleration for 5 seconds before coming to rest at the road block. Find the average velocity of the minibus during the 5 seconds

19. Ordina Tre automobili accelerano mentre percorrono un tratto rettilineo di strada: auto 1: passa da \( 25 \mathrm{~m} / \mathrm{s} \) a \( 35 \mathrm{~m} / \mathrm{s} \) in 10 s auto 2: passa da 0 a \( 30 \mathrm{~m} / \mathrm{s} \) in 15 s auto 3: passa da \( 32 \mathrm{~m} / \mathrm{s} \) a \( 12 \mathrm{~m} / \mathrm{s} \) in 5 s Ordinale per accelerazione crescente.

In one of the processes on the production line at a Sugar Mill, a quantity of gas occupying an original volume of \( 1500 \mathrm{dm}^{3} \) and at an original temperature of \( 300^{\circ} \mathrm{C} \) is expanded adiabatically to a temperature and pressure of \( 135^{\circ} \mathrm{C} \) and 200 kPa respectively. After this adiabatic expansion the gas is heated at constant volume until a pressure of 300 kPa is reached. Given: \( \mathrm{R}=0.286 \mathrm{~kJ} \cdot \mathrm{~kg}^{-1} \cdot \mathrm{~K}^{-1} ; \quad \mathrm{C}_{\mathrm{p}}=1.001 \mathrm{~kJ} \cdot \mathrm{~kg}^{-1} \cdot \mathrm{~K}^{-1}, 1 \mathrm{dm}=10^{-1} \mathrm{~m} \) Assist the production supervisor to: 1.1 Draw a fully labelled \( \mathrm{P}-\mathrm{V} \) diagram for this multi-process system. 1.2 Find the mass of the gas and pressure of the gas before the adiabatic expansion process. 1.3 Find the final volume and final temperature after both processes. 1.4 Find the specific work and specific heat transferred after both processes.

(5) Andrea corre i 100 m col tempo di \( (13450 \pm 8) \mathrm{ms} \). Il suo tempo di reazione ai blocchi di partenza è \( (0,26 \pm 0,03) \mathrm{s} \). Calcola il tempo effettivo impiegato da Andrea per coprire la distanza di 100 m . \( [(13,19 \pm 0,04) \mathrm{s}] \)

4. An Electric Water Heater draws 65 A from a 400 V generator source. The heater is operated on the average 9 hours every day. a) How much power does the heater consume? b) How much energy in KWH does the heater consume in three weeks ( 21 days)? c) At \( \$ 0.17 \) per KWH, how much does it cost to operate this heater for three weeks ( 21 days) period d) This same Electric Water Heater is being used to heat 5.0 Kg of water for industrial purpose every 4 minutes. If \( 80 \% \) of the heat during the 4 minutes is absorbed by the water, what is the change increase in the water temperature during this period of time? Cp of water \( =4180 \mathrm{~J} / \mathrm{Kg}^{\circ} \mathrm{C} \)

\( \left. \begin{array} { c } { L = L _ { 0 } \sqrt { 1 - \frac { v ^ { 2 } } { c ^ { 2 } } } } \\ { = 90 \sqrt { 1 - \frac { ( 0.8 C ) ^ { 2 } } { ( 3 \times 10 ^ { 8 } ) ^ { 2 } } } = 54 m } \end{array} \right. \)