DHS 2023 JC1 Physics Revision (Set B)

Name: Index Number: Class: DUNMAN HIGH SCHOOL Holiday Revision Set B Year 5 Topic LO Q1 Measurement Kinematics (c), (l) (g) / 9 Q2 Kinematics (a), (b), (c) / 8 Q3 Dynamics (a), (f), (g) / 7 Q4 Motion in a Circle (b), (e), (f) / 8 Q5 Gravitational Field (g), (h) / 5 Q6 Oscillations Work, Energy and Power (e) (c), (f), (g) / 8 Q7 Oscillations (b), (c), (f), (g) / 13 Q8 Current of Electricity (b), (f), (g), (j), (k) / 18 Total: / 76

2 @ DHS 2023 1 An army tank fires a bomb at an initial speed of 800 m s −1 at an angle of elevation of α as shown in Fig. 1.1. The bomb is released at a height 300 m above the ground of the valley. Assume air resistance is negligible. (a) Determine the minimum height, in terms of α and g, which an airplane can fly above the ground of the valley without being hit by the bomb. minimum height = ………………….. m [2] (b) Show that the horizontal distance, x, travelled by the bomb is gx 2sin640000= [2] tank α 300 m valley Fig. 1.1 800 m s-1

3 @ DHS 2023 (c) The bomb exploded after travelling the distance in (b). The spherical shockwave produced expands as shown in Fig. 1.2. The radius R of the shockwave, at time t after the explosion, is related to the energy E released and the density  of the surrounding medium according to the equation 0.2 0.2 zR E t −= where z is a constant to be determined. (i) Determine the value of z. z = ………………….. [2] (ii) If R = (80 ± 2) m at t = (0.006 ± 0.001) s , and the density  = (1.2 ± 0.1) kg m −3, calculate the energy released E, with its appropriate uncertainty. E = ……………±…….…….. J [3] Fig. 1.2

4 @ DHS 2023 2 (a) Define velocity. ………..………………………………………………………………………………...………... ………..…………………………………………………………………………………….....[1] (b) A car travels along a long flat road. The velocity -time graph representing the motion of the car is shown in Fig. 2.1 below. Fig. 2.1 (i) Assuming that the car has zero displacement at t = 0 s, find the displacement of the car at t = 11 s. displacement =..………………………….. m [2] displacement =..………………………….. m [2] 2 11 12 −18 v / m s−1 t / s 4 7

5 @ DHS 2023 (ii) Draw a well -labelled displacement-time graph for the motion of the car in Fig. 2.2 below. [3] (iii) Draw a well-labelled acceleration-time graph for the motion of the car in Fig. 2.3 below. [2] s / m t / s 2 7 11 4 a / m s −2 t / s 2 7 11 4 Fig. 2.3 Fig. 2.2

6 @ DHS 2023 3 A toy rocket consists of a plastic bottle which is partial ly filled with water. The space above the water contained compressed air, as shown in Fig. 3.1. Fig 3.1 At one instant during the flight of the rocket, water of density  is forced through the nozzle of radius r at speed v relative to the nozzle. (a) State Newton’s 3rd Law. ……………………………………………………………………………………………………….. . …………………………………………………………………………………………………….. [1] (b) Given that the mass of water ejected per unit time from the nozzle is r2v show that the accelerating force F acting on the rocket is given by the expression F = r2v2 – mg where m is the mass of the rocket and its contents at the instant considered [3] compressed air water nozzle

7 @ DHS 2023 (c) The toy manufacturer recommends that the rocket should contain about 550 cm3 of water before take-off. If the initial air pressure is 1.6 × 10 5 Pa, all of this water will be expelled and the pressure is just reduced to atmospheric pressure as the last of the water is expelled. However, on one flight, the initial volume of water was 750 cm 3 but the initial air pressure in the rocket was still 1.6 × 10 5 Pa. State, without calculation but with a reason, the effect of this increased volume of water on (i) the initial thrust …………………………………………………………………………………………….. ……………………………………………………………………………….………... [1] (ii) the initial acceleration …………………………………………………………………………………………….. ……………………………………………………………………………….………... [1] (iii) the maximum height reached …………………………………………………………………………………………….. ……………………………………………………………………………….………... [1] 4 A horizontal flat plate is free to rotate about a vertical axis through its centre as shown in Fig. 4.1. Fig. 4.1 (a) A penny of mass 3.10 g rests on a small block of mass 20.0 g. The penny and block are then placed on the plate with each centre of mass 12.0 cm from the axis of rotation. The speed of rotation of the plate can be gradually increased from zero. plate penny block

8 @ DHS 2023 The maximum frictional forces F1 between the plate and the block and F2 between the penny and the block are given by the expressions F1 = 0.40 (W1+W2) F2 = 0.52 W2 where W1 and W2 are the weights of the block and penny respectively. (i) Calculate the angular velocity when the block, with the penny, starts to slide. angular velocity = ………………………………. rad s−1 [2] (ii) Calculate the angular velocity when the penny starts to slide. angular velocity = ………………………………. rad s−1 [2] (iii) Hence, d etermine the maximum number of revolutions of the plate per minute for both the block and the penny to remain on the plate. maximum number of revolutions per minute = ……………………. min−1 [2] (b) The plate in (a) is covered, when stationary, with mud. Suggest and explain whether mud near the edge of the plate or near the centre will first leave the plate as the speed of rotation of the plate is slowly increased. …………………………………………………………………………………………. …………………………………………………………………………………………. ……………………………………………………………………………………... [2]

9 @ DHS 2023 5 (a) Define gravitational potential at a point in a gravitational field. …………………………………………………………………………………...…. ……………………………………………………………………………………[1] (b) Four identical masses, each of mass m, are arranged symmetrically about a light circular ring of radius R as shown in Fig. 6.1. Point P is at a distance h from the centre O of the ring along the central axis of the ring. Fig. 6.1 Derive an expression in terms of m, h, R and the gravitational constant G, for (i) the gravitational potential at point P, [2] (ii) the minimum velocity that a mass placed at P needs to be projected with, such that it is able to escape the gravitational field of the four masses. velocity = ………………………………m s−1 [2] h m m m m P O R

10 @ DHS 2023 6 The variation of displacement x of the acceleration a of a system is shown in Fig 8.1. Fig. 8.1 (a) Explain how it may be deduced that the oscillations of the system are simple harmonic. …………………………………………………………………………………..……………. …………………………………………………………………………………..……………. …………………………………………………………………………………..……………. ……………………………………………………………………………………………..[3] (b) An object of mass m1 = 9.00 kg is in equilibrium while connected to a light spring of spring constant k = 100 N m−1 that is fastened to a wall as shown in Fig. 8.2.1. A second object m2 = 7.00 kg is slowly pushed up against m1, compressing the spring by the amount A = 0.200 m (see Fig. 8.2.2). -20 -15 -10 -5 0 5 10 15 20 -6 -4 -2 0 2 4 6 x / mm a / m s−2 k k m1 m1 m2 A Fig. 8.2.1 Fig. 8.2.2