Physics Questions & Answers

6. Berapa energi yang dihasilkan oleh suatu mesin yang berdaya 250 Watt selama 2 jam? 3

a) An air jet is flying with a constant speed at an angle of \( 30^{\circ} \) above the horizontal as indicated in the figure below. The weight \( \vec{W} \) of jet has magnitude \( \mathrm{W}=86500 \mathrm{~N} \) and its engine provide a forward thrust \( \overrightarrow{\boldsymbol{T}} \) of magnitude \( \mathrm{T}=103000 \mathrm{~N} \). In addition, the lift force \( \vec{L} \) (directed perpendicular to the wings) and the force \( \vec{R} \) of air resistance (directed opposite to the motion) act on the jet. Illustrate the forces acting on the air jet by means of a free body diagram and determine the magnitude of \( \vec{R} \) and \( \vec{L} \). (4)

طبق قانون خنک‌کنندگی نیوتن، اگر دمای یک مایع در ابتدا 90 درجه سانتی‌گراد باشد و بعد از چند دقیقه به 50 درجه کاهش یابد، دمای محیط چقدر می‌تواند باشد اگر این کاهش در مدت 5 دقیقه اتفاق افتاده باشد؟

37 Moto armonico Un oggetto si muove di moto armonico semplice con periodo \( T \) e ampiezza \( A \). Quanto tempo impiega per spostarsi da \( x=A \) a \( x=A / 2 \) ? Esprimi il risultato in funzione di \( T . \quad[t=T / 6] \)

f. You still walked to the right, but for whatever reason, you chose the direction left to be the \( +x \) direction. Keep \( x_{1}=0 \mathrm{~m} \). What changes?

f. You still walked to the right, but for whatever reason, you chose the direction left to be the \( +x \) direction. Keep \( x_{1}=0 \mathrm{~m} \). What changes? g. If you just had the snapshots without the video or actually seeing the walk, could you tell if the walker ever changed speed or direction? and/or direction, but still was at the same positions and times (same snapshots), what results would change?

e. Put velocity vectors on your sketch at all four instants (states). Also put the following displacement vectors on your sketch: \( \Delta x_{1 \rightarrow 2}, \Delta x_{1 \rightarrow 4}, \Delta x_{2 \rightarrow 3}, \Delta x_{2 \rightarrow 4} \) f. You still walked to the right, but for whatever reason, you chose the direction left to be the \( +x \) direction. Keep \( x_{1}=0 \mathrm{~m} \). What changes? g. If you just had the snapshots without the video or actually seeing the walk, could you tell if the walker ever changed speed or direction? and/or direction, but still was at the same positions and times (same snapshots), what results would change?

At night, when it gets cold outside, Pearl closes the curtains on the window in her room, Pearl's curtains reach down to the floor and are close to the wall. Explain why the layer of air between the curtain and the window reduces heat transfer by conduction through the glass of the window pane. In your answer, you should: explain, in terms of particle theory of matter, how heat transfer by conduction works compare and contrast conduction through air and glass.

e. Put velocity vectors on your sketch at all four instants (states). Also put the following displacement vectors on your sketch: \( \Delta x_{1 \rightarrow 2}, \Delta x_{1 \rightarrow 4}, \Delta x_{2 \rightarrow 3}, \Delta x_{2 \rightarrow 4} \)

e. Put velocity vectors on your sketch at all four instants (states). Also put the following displacement vectors on your sketch: \( \Delta x_{1 \rightarrow 2}, \Delta x_{1 \rightarrow 4}, \Delta x_{2 \rightarrow 3}, \Delta x_{2 \rightarrow 4} \) f. You still walked to the right, but for whatever reason, you chose the direction left to be the \( +x \) direction. Keep \( x_{1}=0 \mathrm{~m} \). What changes? g. If you just had the snapshots without the video or actually seeing the walk, could you tell if the walker ever changed speed or direction? and//or direction, but still was at the same positions and times (same snapshots), what results would change?