Answer: Option D View the video tutorial for the explanation

Solutions: Option B You can view the video tutorial here or the written solutions below.

Note: Non-uniform plank means the CG of the plank is not at its centre a) Find the weight of the boy. b) How far is the centre of gravity of the plank from point A? Solutions: a) 300 N and b) 6.67 m Click on the video tutorial if you can’t derive the 2 equations.

Double-insulated appliances are common around us. The air purifiers in our classroom are one good example. In these appliances, only two wires are needed, namely Live and Neutral wires . Earth wire is not required as the casing is made of insulator like plastic for this case. The classic air purifier in our classroom The “double squares” symbol means that this appliance is double-insulated. As you see, the earth wire is not required.

Pressure of a fixed mass of gas, P, is inversely proportional to the volume of the gas, V, when the temperature is held constant. P inversely proportional to V P = k/V , where k is a constant. PV = k With these concepts, you should be able to sketch the various graph. Do not memorise them. Use your concepts from Maths to help you to recall instead.

Transverse waves  are waves in which the  direction of the wave  is  perpendicular  to the direction of the vibration . e.g Light, water, and any waves in the electromagnetic spectrum Longitudinal waves  are waves in which the  direction of the wave  is  parallel  to the  direction of the vibration . e.g Sound (includes ultrasound or infrasound) Wave equation: V = fλ  In the videos below, the speed of wave is constant. Hence frequency is inversely proportional to wavelength.  [f increases, λ decreases, and vice versa]

Reflection of light using a mirror Refraction of light using various shaped optical mediums Total Internal Reflection (TIR) using a semi-circular perspex For Total Internal Reflection (TIR) to occur: 1) angle of incidence i is greater than the critical angle c 2) the light is travelling from an optically denser medium towards a less dense medium

Solutions: Option B

A rock is thrown vertically upwards with a velocity of 29.4 m/s from the top of a building 78.4 m high. After how long will the rock reach the ground below? (Take g = 10 m/s2) Many are familiar with calculation when ball is released from rest. This question involves ball being thrown upwards, and then it falls to the ground. To solve this question, just treat the motion as 2 separate parts. 1) Ball going up to max height, 2) Ball going down (similar to ball released from rest from highest point)

The speed-time graph of Car A and Car B, along a straight road over 4 seconds is shown below. a) Calculate the acceleration of Car A and Car B over the 4 seconds.     Ans: a of Car A = 3 ms-2 and a of Car B =0.75 ms-2 Car A overtakes Car B at time t seconds. b) Derive two separate expressions for the velocities of Car A and Car B at the point when Car A overtakes Car B, in terms of t. Ans: Va = 3t    and    Vb = 3 + 0.75t c) Calculate the time t when Car A overtakes Car B.    Ans: t = 2.67s Solutions for (a) and (b) Solutions for (c)