AQA AS Physics C9 Force And Momentum Kerboodle Answers

C9.1 Momentum and impulse AQA AS Physics C9 Force And Momentum Kerboodle Answers: Page No. 157

1.Ans- a i 1.2 x 10-18 kgms-1 ii0.050kgms-1 iii 14kgms-1 b i 6.0kg ii 20ms-1 2.Ans- a 3.6 x 105 kgms-1 b 60s 3.Ans- a 5.4 x 106 kgms-1 b 45 s 4.Ans- a9.0 x 103 kgms-1 b i -8.4 x 103 kg ms-1 ii 1.0 ms-1

9.2 Impact forces AQA AS Physics C9 Force And Momentum Kerboodle Answers: Page No. 160

1. a the initial momentum of the lorry 1600kg ms-1 b the force of the impact. 3200N 2. a the change of momentum of the car due to the impact 3000kgms-1 b the impact force. 7.5kN 3. a the change of momentum -4.2 x 10-23 kgms-1 b the force on the molecule. -1.9 x 10-13 N 4. -2.1 x 10-23 kgms-1

9.3 Conservation of momentum AQA AS Physics C9 Force And Momentum Kerboodle Answers : Page No. 163

1. 0.72 m s-1 2. 0.7ms-1 in the same direction 3 . 0.05 m s-1 in the direction the 1.0 kg trolley was l 1.0 x 107m2 moving in 4. -0.63 m s-1 in the opposite direction to its initial direction.

9.4 Elastic and inelastic collisions AQA AS Physics C9 Force And Momentum Kerboodle Answers: Page No. 165

1.a i it rebounds to the same height ii it rebounds to a lesser height. In aii, the ball is released from a height of 1.20m above the surface and it rebounds to a height of 0.90 m above the surface. Show that of its kinetic energy is lost in the impact, 2. a the velocity of the vehicles immediately after impact 9.0ms-1 in the same direction b the loss of kinetic energy due to the impact. 24kJ 3.a the speed and direction of the 1.0 kg ice puck after the collision 1.1 ms-1 in the reverse direction b the loss of kinetic energy due to the collision. 20J 4. a’i 1.0 ms-1 ii Show that the collision was an elastic collision. b The driver of the 250kg car experiences a force from his/her car which slows him/her down; the other driver experiences a force from his/her car that accelerates him/her.

9.5 Explosions AQA AS Physics C9 Force And Momentum Kerboodle Answers : Page No. 167

1 .0.35 ms-1 2. a 0.25ms-1 ;the mass of A and X was greater 1 than the mass of B. so B moved away faster. b Show that the mass Of X must have been 0.10 kg. 3. a i 0.10 ms-1 ii15 mJ b 0.19ms-1 4.a the speed at which the rock was thrown from the boat 9.0ms-1 b the kinetic energy gained by i the boat 1.1 J ii the rock. 81 J

Practice questions: Page No. 168-169

1. (a)In an inelastic collision, kinetic energy is not conserved (b) (i) the momentum of the ball before the collision Momentum p = mv gives p = 0.12 × 18 = 2.16 N s (or kg m s-1) (ii) the momentum of the ball after the collision p = 0.12 × (−15) = −1.8 N s (or kg m s-1 ) (iii) the total change of momentum of the ball Change in momentum = 2.16 − (−1.8) = 3.96 N s (or kg m s-1 ) (iv) the average force acting on the ball during contact With the bat (v) the kinetic energy lost by the ball asa result 01 the collision. 2 . (a) (b) Impulse = change of momentum ∴0.135 = mA × 0.60 from which mA = 0.225 kg or 0.22 kg or 0.23 kg (c) The final total momentum of the system is zero 3.(a) Calculate the momentum of the engine. p = mv = 6.2 × 104 × 0.35 = 2.17 × 104 N s (or kg m s−1 ) or 2.2 × 104 N s (b) Initial momentum of engine = combined momentum after coupling ∴2.17 × 104 = 10.2 × 104 v gives v = 0.213 m s-1 or 0.21 m s-1 4. (a) ) Two quantities that are conserved: • momentum • kinetic energy (b) A gas molecule makes an elastic collision with the walls of a gas cylinder. The molecule is travelling at 450ms—l at right angles towards the wall before the (i) Magnitude of velocity is 450 m s−1 The direction is away from the wall at 90 ° to it (or in the opposite direction to the initial velocity). (ii) (c) • Force is exerted on the molecule by the wall • Molecule experiences a change in its momentum • Molecule must exert a force on the wall which is equal and opposite to the force produced by the wall on the molecule, by Newton’s third law of motion 5.(a) b (i) (ii) 6 (a) The shaded area represents impulse (or change in momentum). (b) 7.(a) The total momentum of a system of objects remains constant provided that no external resultant force acts on the system (b) (i) (ii) (iii) Banner 7

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