1. B 11. A 21. C 2. C 12. B 22. E 3. A 13. E 23. D 4. D 14. A 24. D 5. D 15. A 25. C 6. C 16. B 26. D 7. B 17. A 27. A 8. A 18. C 28. E 9. C 19. A 29. D 10.A 20. E 30. E
31.a. Each rope exerts a force in the direction of travel. To calculate the component of the force in the direction of travel use basic trigonometry. The force from each rope is: FDirection of travel= FResultantcos20o FDirection of travel= 150xcos20o FDirection of travel= 140.95N The total force from both ropes (Ftotal) can now be calculated. Ftotal= 2x140.95N Ftotal= 281.9N b. As the boat is moving at constant speed, and in a straight line, the frictional force must be equal in magnitude to the pulling but acting in the opposite direction to the pulling force. Ffriction= -281.9N (-ve sign indicates direction) 32.a. b. Newton's first law states that: "an object will remain at rest or move with a constant velocity in a straight line unless acted upon by an unbalanced force". This means there are no unbalanced/resultant forces acting on the balloon, as it is at rest. 33. To determine the type of collision the kinetic energy before the collision [Ek(before)] and the [Ek(after)] must be considered. Elastic collision => Kinetic energy conserved. Inelastic collision => Kinetic energy not conserved. Before collision Total [Ek(before)]= 0.036J +0J Total [Ek(before)]= 0.036J Total [Ek(after)]= 0.009J +0.018J Total [Ek(after)]= 0.027J Kinetic energy is not conserved, therefore, the collision is inelastic. 34.a. Wave period(T) = 4x2.5ms T = 10x10-3s f=1/T f=1/10x10-3s f=100Hz b. The amplitude of the waves displayed on the oscilloscope will be unchanged, but, five complete waves will now appear on the screen. 35.a. V = E-Ir or V = -rI + E Compare this to: y = mx + c y = V m = -r x = I c = E m = (4-1)/(1-3) = 3/-2 = -1.5 =>r = -m = 1.5 =>r = 1.5W b. I = E/r E is the emf of the battery, found by noting where the graph cuts the voltage axis. E = 5.5V =>I = 5.5/1.5 I = 3.67A 36.a. The refractive index of paraffin(np) is found by calculating the ratio of the speed of light in air to the speed of light in paraffin. np = 3x108/2.1x108 np = 1.43 b. The frequency of the light is unchanged when moving from air into paraffin. f=4.85x1014Hz 37.