CJC 2015 A level H2 Physics Answers

1 H2 Physics 9646 – 2015 A Level Exam Paper 1 1 Keywords:  Base quantity  SI units Answer: A 2 Keywords:  Average speed Essential Questions:  How do you determine the average speed of the vehicle?  How do you determine the total distance travelled from a speed-time graph? Answer: D 3 Keywords:  Thrown Horizontally  Air resistance is negligible Essential Questions:  What are the forces acted on the stone after it leaves the cliff?  Which component of the velocity is affected? Use kinematics equations to determine the x and y components of the final velocity just before it hits the surface of the water. Answer: C 4 Keywords:  Propelling force is constant  Water runs out of the tanker Essential Questions:  What happens to the mass of the water tanker?  What are the changes in the variation of the resistive forces and ultimately, the net force? Answer: A 5 Q: What physics relationships hold for a head-on elastic collision?  (1): Total momentum is conserved throughout the motion AND  (2): Total KE before the collision equals to total KE after the collision.  (3): A consequence of solving (1) and (2) simultaneously is that the Relative velocity of approach between the two bodies before the collision equals to their Relative velocity of separation after their collision..\ Take direction to the right as positive. Applying (1), we get: mu1 + m(-u2) = mv1 + mv2  u1 – u2 = v1 + v2  Tallies with option B Applying (2), we get: ½ m u1 2 + ½ m u2 2 = ½ m v1 2 + ½ m v2 2  u1 2 + u2 2 = v1 2 + v2 2  Tallies with option C Applying (3), we get: u1 – (-u2) = v2 – v1  u1 + u2 = v1 – v2

2  No such option. Answers: B and C Note: the proposed answer by Cambridge was C, but later found to be an error as both B and C are valid. 6 Keywords:  Diagram showing a section of canal  Extra weight Essential  What is the meaning of extra weight ?  If there is extra weight, where does it comes from?  Before the barge cross the bridge, how much weight does the bridge supports?  When the barge is at the bridge, what are the forces acting on the barge? Proposed Solution: When the barge moves onto the bridge (aqueduct), it is displaces an amount of water and the weight of the displaced water is equal to the weight of the barge. The displaced water moves off the aqueduct as the boat moves onto it. Thus there is no extra weight supported by the bridge. Answer: A 7 Keywords:  Held below the surface of water  Released and floats to the surface  Fully submerged  Floating Essential questions 1. How forces are balanced when the ice is floating? 2. How can weight be expressed in terms of density and volume? 3. What expressions can be written when fully submerged and floating? Proposed Solution: Let the volume of ice be Vice = A(Surface area) x H (thickness) , ρice = density of ice, ρw = density of water, d = height of