4. (1.5 marks} For a rotating object. a] If the angular speed is positive the angular acceleration must be positive as well. b] A zero angular acceleration is possible with non-zero angular speed c If the angular speed is zero then the angular acceleration must be zero as well None of the above are true J d) All of the above are true 8) 5. (1.5 marks) A adder leans against a wall at angle 8. The other end rests on a horizontal surface. The ladder will be in static equilibrium if a) There is suf'icient friction between the ladder and the wall b) There is suf'icient friction between the ladder and the floor c) There is sufcient friction between the ladder and either the wall or the floor. You need friction on at least one surface. but it doesn't matter which one. d) There is suicent friction between the ladder and both surfaces. If either surface is frictionless. the ladder will slip. e) None of the above 6. (1.5 marks) A torque acts on a disk= which can pivot about its centre of mass. as shown. The magnitude of the torque increases linearly with time. W'hich of the following statements must be true? a) The disk is rotating in the clockwise direction b} The disk's angular speed will change at a constant rate. 0} The disk's angular acceleration is in the counterclockwise direc- tion. (I) At some point in the future, the disk will be rotating in the clock- wise direction. e} Either none of the above, or more than one of the above, are true. 7. (1.5 marks) A simple harmonic oscillator with period T has speed 7: at some point in time. The next time it has the same speed a] Must be a period T later 6" ) Must be half a period later c Must be one quarter of a period later. {3. l ) Can occur at any value of t between zero and 372 (inclusive). ) e None of the above. 8. (1.5 marks) If you superpose two waves with the same amplitude and wavelength. the resulting amplitude will be a) Twice the amplitude of each wave b) Four times the amplitude of each wave c) Some value between zero and four times the amplitude of each wave d] Some value between zero and twice the amplitude of each wave ) e Any of the above is possible. A Concept Questions: Answer all questions on the computer card provided. 1. (1.5 marks) In the diagram below, a block of mass m is attached by a string to a block of unknown mass M2 on an inclined plane. What is the magnitude of the normal force acting on mass m? a) N = mg b) N > mg C) N