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UNIVERSITY OF SOUTH AUSTRALIA School of Electrical & Information Engineering (Applied Physics) ENGINEERING PHYSICS QUIZ 3 [ week 13 ] Time: 20 minutes

Marks: 20 Name .....................................................................................

QUESTIONS ( 8 MARKS )

ANSWERS

1. Consider a point on a bicycle wheel as the wheel turns about a fixed axis, neither speeding up nor slowing down. A. B. C. D.

Compare the linear and angular accelerations of the point. Both are zero. Only the angular acceleration is zero. Only the linear acceleration is zero. Neither is zero.

2. Mountain roads spiral around the mountain rather than going straight up to A. B. C. D. E.

Reduce the amount of work required Reduce the amount of power required Reduce the time taken Reduce the energy required None of the above

3. A karate expert executes a swift blow and breaks a cement block with a bare hand. The magnitude is the same for A. B. C. D.

the impulse on both the block and the expert’s hand, the time of impact on both the block and the expert’s hand, the force on both the block and the expert’s hand, all of the above

4. The spectral distribution shown exhibits characteristic x-ray peaks. These arise from… A. B. C. D. E.

electron interaction with the nucleus core level ionisation photon absorption all of the above none of the above

QUESTIONS & PROBLEMS ( 14 MARKS ) Problem 1 (5 marks) After its release at the top of the first rise, a roller coaster car moves freely with negligible friction. The roller coaster has a circular loop of radius 20.0m. The car barely makes it around the loop: at the top of the loop the riders are upside down and feel weightless. 1. Find the speed of the roller coaster at the top of the loop. 2. Find the speed of the roller coaster at the bottom of the lop and halfway up the loop 3. Find the difference in height between the initial position and the final position, if the final speed is 10.0m/s. ……………………………………………………………………… ………………………………………………………………………

3 R

4 2

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……………………………………………………………………………………… Problem 2 (5 marks) A car traveling at the speed limit (60km/hr) north along Main North Rd reaches the traffic lights at Grand Junction Rd. While traveling through the intersection it is hit by another car traveling east along Grand Junction Rd. The cars stick together after collision and continue with a final speed of 10km/hr along Main North Rd (which makes an angle of 45° with Grand Junction at the intersection. i.e. NE direction). Draw a diagram of this situation (2 marks). What is the initial speed of the car traveling along Grand Junction Rd? (3 marks) ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………