Quizzes > Engp Q1 02

UNIVERSITY OF SOUTH AUSTRALIA Applied Physics - School of Electrical & Information Engineering ENGINEERING PHYSICS QUIZ 1 [ week 3 ] Time: 20 minutes

Name .....................................................................................

QUESTIONS ( 9 MARKS )

Marks: 19/15

ANSWERS

1. The standard SI unit for mass is the A. B. C. D.

atomic mass unit, gram, kilogram, tonne.

2. The prefix micro represents … A. B. C. D. E.

1/100, 1/1000, 1/10,000, 1/100,000, 1/1,000,000.

3. A health conscious student on a bicycle travels 12 km in 40 minutes. The average speed of the student is … A. B. C. D.

0.3 km/hr, 8 km/hr, 18 km/hr, 48 km/hr.

4. Two skydivers jump from the plane at the same instant in time. Skydiver A weighs twice as much as skydiver B and they both forget to put on their parachutes. Neglect air resistance, then which statement below is true? … A. Ski diver A hits the ground before B, B. Ski diver B hits the ground before A, C. they both hit the ground at the same time, D. there is insufficient information in this problem to enable one to determine the answer.

5. The weight of an object.. A. B. E. F.

is the quantity of matter it contains, refers to its inertia, is basically the same quantity as mass but expressed in different units, is the force with which it is attracted to the earth.

6. When a 1 N force acts on an object that has a mass of 1 kg and is able to move freely, the object receives … A. B. C. D.

a speed of 1 ms-1, a velocity of 0.102 ms-2, an acceleration of 1 ms-2, an acceleration of 9.8 ms-2.

7. Which statement is true about the unit vectors i, j and k? A. B. C. D.

Their directions are defined by a left-handed coordinate system, The angle between any two of them is 90o, Each has a length of 1 metre, If i is directed east and j is directed south, k points up out of the surface.

8. A softball player throws a ball vertically upwards and catches it in the same spot when it returns to their mitt. At what point in the ball’s path does it experience zero velocity AND non-zero acceleration at the same time? A. approximately midway on the way up, B. at the top of the trajectory, C. the instant it leaves the players hand, D. the instant just before it arrives back in the mitt.

9. A projectile starts at the coordinate origin and its initial velocity vector makes an angle of 30o with the horizontal. At the instant when the projectile is at its highest point of its trajectory, the position, velocity and acceleration vectors are r, v and a. Which statement is true?

A. B. C. D.

r is parallel to v, r is perpendicular to v, v is parallel to a, v is perpendicular to a.

PROBLEMS ( 10 MARKS ) Question 1 (4 marks) A woman is rowing at 8 km/hr in a river which is 1.5 km wide and in which the current is 5 km/h. (i) In what direction should she row in order to get across the river in the shortest time? Justify your answer. …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… ………………………………………..…………………………………………………………………………… (ii) How long will it take for her to get across the river? ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… Problem 1 (6 marks) As a yup’ee engineering graduates your new Porsche can accelerate from 0 to 100 km/hr in 6.2 seconds. If you take off from the lights (initially stationary), how far down the road does it take to get to the urban speed limit (60 km/hr)? Hint: 1 km/hr = 1000m/60x60s = 1/3.6 m/s

1 ………………………………………..…………………………………………………………………………… s = v0 t +

at 2

2 ………………………………………..……………………………………………………………………………

v f = v 0 + at ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… v 2f = v 02 + 2as ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..…………………………………………………………………………… ………………………………………..……………………………………………………………………………