RI 2020 Y5 H2 Physics TP Section B QP

© Raffles Institution [Turn over Name: ( ) CT Group: 21S0 RAFFLES INSTITUTION 2020 YEAR 5 TERM 3 TIMED PRACTICE 24 June 2020 H2 PHYSICS RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INST ITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES INSTITUTION RAFFLES Section B INSTRUCTIONS TO CANDIDATES Write your name, index number and CT Group. For Examiner’s Use Write your answers to Section B in the spaces provided on the question paper. Section A MCQ / 11 Section B 12 / 11 13 / 11 14 / 12 15 / 12 16 / 11 17 / 12 Deductions Total / 80 This document consists of 15 printed pages.

2 © Raffles Institution 12 (a) A student drains the water from a fully filled rectangular water tank of length L, width w and height h into a drain by using a tube of cross-sectional area A, as shown in Fig. 12.1. The drain is located at a vertical distance d below the surface of the water in the tank. (i) The student proposed that the time t taken to empty a fully filled tank is given by 2 Lwht A gd ××= where g is the acceleration of free fall. Show that the equation is homogeneous. [2] (ii) State two ways why the equation in (i) may be physically incorrect, even though it is homogeneous. 1. 2. [2] h L w d drain tube Fig. 12.1

3 © Raffles Institution [Turn over (b) A wire of uniform circular cross -section has diameter d and length L. When a potential difference V is applied across the ends of the wire, a current I flows through the wire. The resistivity ρ of the material of the wire is given by the expression 2 4 dV L π= Iρ In one particular experiment, the following measurements are made. d = (0.32 ± 0.01) mm L = (50.0 ± 0.1) cm V = (1.60 ± 0.02) V I = (0.23 ± 0.04) A (i) Suggest an instrument that was used to measure d. [1] (ii) Calculate the value of ρ. ρ = Ω m [2] (iii) Calculate the actual uncertainty in ρ. actual uncertainty in ρ = Ω m [2] (iv) State the value of ρ and its actual uncertainty to the appropriate number of significant figures. ρ = ± Ω m [1] (v) Suggest an improvement that can be made to the experiment to reduce the percentage uncertainty in the value of ρ. [1]

4 © Raffles Institution 13 (a) Distinguish between speed and velocity. [1] (b) A ball is thrown from the top of a 50 m tall building at an angle 30° above the horizontal with an initial speed of 7.0 m s−1. The ball lands at a horizontal distance x from the base of the building. In the absence of air resistance, the path of the ball is shown in Fig. 13.1. (i) State the shape of the path. [1] (ii) Show that the time of flight is 3.57 s. [1] 50 m 30° Fig. 13.1 x 7.0 m s−1

5 © Raffles Institution [Turn over (iii) Calculate x. x = m [2] (iv) Determine the velocity of the ball at the instant just before it hits the ground. magnitude of velocity = m s−1 direction of velocity = [4] (c) On Fig. 13.1, sketch the path of the ball if air resistance was present. [2]

6 © Raffles Institution 14 (a) State Newton’s second law of motion. [2] (b) In a safety test on a sports car, a dummy is firmly restrain ed in its seat by means of seatbelts. The car suffers a head- on collision with a wall where both the car and the dummy are brought to rest from a speed of 30 m s –1 at an average deceleration of 80 m s–2. The mass of the car is 1500 kg and the mass of the dummy is 80 kg. (i) Calculate the magnitude of the change in momentum of the car and the dummy. magnitude of change in momentum = N s [2] (ii) Determine the duration of the collision. duration of collision = s [2]

7 © Raffles Institution [Turn over (iii) Using the principle of conservation of linear momentum, state and explain whether the linear momentum of the car and the dummy is conserved in this collision with the wall. [2] (iv) During the collision, the dummy’s head of mass 3.0 kg stays firmly attached to its body. Calculate the average horizontal force exerted by the neck on the dummy’s head. average horizontal force = N [2] (v) Professional race car drivers are usually fitted with a harness as shown in Fig. 14.1. The harness is shaped like a "U", with the back of the "U" set behind the back of the neck and its two arms lying flat along the top and over the driver’s chest. The harness is supported by the shoulders and attached only to the helmet. Fig. 14.1 Suggest, with a reason, how the harness helps to prevent injury to the neck of a driver in a head-on collision. [2] helmet harness arms

8 © Raffles Institution 15 (a) Explain what is meant by the weight of an object. [1] (b) A light spring of force constant 14 N m−1 is attached to a fixed horizontal rod. A solid steel cube of mass 0.070 kg is hung from the end of the spring, and the spring-mass system is in equilibrium as shown in Fig. 15.1. Fig 15.1 Show that the extension in the spring is 0.049 m. [1] (c) The spring-mass system is lowered into a beaker of water of density 1000 kg m −3 as shown in Fig. 15.2. 75% of the steel cube is submerged in the water. Fig. 15.2 (i) On Fig. 15.2, draw and label the forces acting on the steel cube. [3] horizontal rod attached to retort stand spring beaker of water ground steel cube horizontal rod attached to retort stand spring

9 © Raffles Institution [Turn over (ii) Calculate the upthrust acting on the steel cube. [Density of steel = 7780 kg m−3] upthrust = N [3] (iii) Hence, calculate the extension in the spring with the steel cube submerged. extension = m [2] (iv) An identical spring mass system is now lowered into a container of oil with 75% of the steel cube submerged. State and explain in terms of forces whether the new extension in the spring is now longer or shorter than your answer in (c)(iii). [2]

10 © Raffles Institution 16 (a) (i) Define work. [1] (ii) Hence, derive the equation Ep = mgh, for the change in gravitational potential energy of a mass m, when moved a vertical distance h upwards against a uniform gravitational field of field strength g.