THEME 1: NEWTON MECHANIC Learning Standard 1.4 ELASTICITY 1.4.1 Describe elasticity 1.4.2 Experiment to investigate relationship between force F and extension of spring, x 1.4.3 Communicate about the law related to force, F and extension of the spring, x 1.4.4 Solve problems involving force, F and extension of spring, x 1.1 RESULTANT FORCE 1.1.1 Describe resultant force 1.1.2 Determine the resultant force 1.1.3 Communicate about resultant force, F when an object is: (i) stationary, F = 0 N (ii) moving with constant velocity, F = 0 N (iii) moving with contstant acceleration, F ǂ 0 N 1.1.4 Solve problems involving resultant force, mass and acceleration of an object. 1.2 RESOLUTION OF FORCES 1.2.1 Describe resolution of forces 1.2.2 Solve problems involving resultant force and resolution of forces 1.3 EQUILIBRIUM OF FORCES 1.3.1 Explain forces in equilibrium 1.3.2 Sketch a triangle of forces in equilibrium 1.3.3 Solve problems involving forces in equilibrium

F2 F = F1 - F2 Activity 1 Aim: To generate idea of resultant force and to determine its direction. Apparatus: Two spring balances and a 1 kg weight Material: A wooden block with a hook at both ends 1. Set up the apparatus as shown. 2. Pull the wooden block using spring balance A and spring balance B in opposite directions, so that the wooden block does not move. 3. Record the readings of the spring balance. 4. Repeat steps 2 and 3 so that the wooden block moves (a) to the right (b) to the left Condition of the wooden block Reading of spring balance A / N Reading of spring balance B / N Stationary Moves to the right Moves to the left Discussion 1. Compare the readings of the two spring balances when the wooden block is: (a) stationary: …………………………………… (b) moving to the right: ………………………… (c) moving to the left: …………………………… 2. State the relationship between the direction of motion of the wooden block and the direction of the force acting on the wooden block. ……………………………………………………………… Activity 2 Aim: To determine the resultant force produced when two forces are acting on an object on a plane. Situation 1: Two forces acting on an object in the same direction. 1. Calculate the resultant force. Which direction does the object move? 2. A horse pulls a cart with a force of 500 N. A farmer helped the horse by pushing the cart with 200 N force. What is the resultant force? Situation 2: Two forces acting on an object in the opposite direction 3. Calculate the resultant force. Which direction does the object move? 4. A horse pulled a cart with 500 N force. A farmer pulled the same cart with 200 N force but in opposite direction. What is the resultant force? 1.1

Situation 3: Two forces that act on an object perpendicular to each other. 5. Consider the two forces as the sides of a rectangle. (a) Complete the diagram with the sides representing the two forces that are perpendicular to each other. (b) Draw the diagonal of the rectangle that represents the resultant force, F of the two forces. (c) Calculate the length of the diagonal using Pythagoras’ Theorem. (d) Calculate the angle between the diagonal and one of the sides of the rectangle. Situation 4: Two forces acting on an object in directions that are not perpendicular to each other Pull a wooden block with forces of different magnitude and direction. Observe the effect of the combination of the two forces on the block. Observation: …………………………………………………….……… …… Parallelogram of forces method to determine resultant force involving two forces acting at a point at an angle. F1 = 1000 N F2 = 2000 N Choose a suitable scale to draw lines that represent the magnitude of the forces. scale: 1 cm = …… STEP 1: Using ruler and protractor draw the two forces F1 and F2 from a point STEP 2: complete the parallelogram STEP 3 Draw the diagonal of the parallelogram. The diagonal represent the resultant force, F in magnitude and direction. Measure the length of the diagonal and calculate the magnitude of the resultant force using the scale you have choosen Measure the angle, θ

Triange of forces method Choose a suitable scale to draw lines that represent the magnitude of the forces. scale: 1 cm = …… STEP 1: By using a ruler and a protractor, draw the force F1 followed by force F2 to form two sides of a triangle. STEP 2: complete the triangle. The third side represents the resultant force, F STEP 3 Measure the length of side F and calculate the magnitude of the resultant force using the scale you have chosen. Excersice 1: 1. Parallelogram Method Set a scale. Using a ruler and protractor, draw the two forces, F1 and F2 from a point O. Complete the parallelogram. Draw the diagonal of the parallelogram. The diagonal represents the resultant force, F in magnitude and direction. 2. Triangle method Set a scale. Using a ruler and protractor, draw the first force, F1 from a point O. Draw the second force, F2 from the head of F1. Complete the triangle by drawing a line from the tail of F1 to the head of F2. The diagonal represents the resultant force, F in magnitude and direction. 3. The figure above shows an aerial view of two boats are pulling a ship. The forces exerted are F1 = 4000 N and F2 = 3000 N with the angle between the two cables is 50⁰. Determine the magnitude of the resultant force on the ship. In which direction will the ship move?

4. Complete the diagram to show the resultants force by using triangle method. 5. Total weight of the lift and passengers are 6 400 N. The tension of the lift cable is 8 000 N. What is the resultant force acting on the lift? 6. Two forces of 8 N and 4 N acted on an object. Find: (a) Maximum magnitude: …………… (b) Minimum magnitude: …………… Activity 3 Aim: To determine the magnitude and direction of the resultant force of two forces that make an angle with each other. Apparatus: Three spring balance, thread, metal ring, mahjong paper and meter ruler. 1. draw a parallelogram on a mahjong paper to show resultant force for 4 N and 3 N forces at right angle with each other. Use scale: 10 cm = 1 N. 2. Measure the resultant force, F. 3. Tie the thread to the three spring balances. Tie each end to a metal ring. 4. 3 students will pull the spring balances on the parallelogram until the metal ring is at rest. Refer to the diagram below. Reading of spring balance 1 = 4 N and the reading of the spring balance 2 = 3 N. Record the reading of spring balance 3. Result: Reading of spring balance 1 Reading of spring balance 2 Readig of spring balance 3 4 N 3 N Discussion: 1. What is the resultant force, F? ………………. 2. What is the direction of the resultant force of the two forces that act on the metal ring through spring balance 1 and spring balance 2? ……………………………………………………………… 3. Why is the magnitude of the force acting on the metal ring thorugh pulley C equal to te magnitude of the resultant force? ………………………………………………………………

Activity 4 Aim: To discuss the resultant force that acts on an object with the aid of free body diagrams. 1. A free body diagram of an object is a diagram that shows all the forces acting on that object only. Show and label all the forces act on an object. Free body diagram Name the force R = W = W = T = Direction of motion R = W = T = f = Newton’s Second Law of Motion can be expressed as F = ma. If a number of forces act on an object at the same time, F represents the resultant force on the object. 2. Complete table below to the information on the magnitude of the resultant force on an object in different states of motion. States of motion Comparison between forces acted a. Car in a stationary state velocity, v = ____ Acceleration, a = ____ Resultant force, F = ___ W R Weight normal reaction force b. Car moving with a uniform velocity velocity, v = ____ Acceleration, a = ____ Resultant force, F = ___ W R Weight Normal Reaction force T f engine frictional force thrust c. Car moving with a uniform acceleration velocity, v = ____ Acceleration, a = ____ Resultant force, F = ___ W R Weight Normal Reaction Force T f Engine frictional Thrust force Resultant force, F = ___ Activity 5 Aim: Solving Problems Involving Resultant Force, Mass and Acceleration on an Object A. Object moves horizontalaly or verticaly 1. Figure shows a coconunt of mass 2.0 kg falling with an accelaration of 9.0 ms-2 . (a) Sketch the free body diagram of the coconut. (b) Calcultate the resultant force acting on the coconut.

ma mg > R F = ma F = mg – R = ma R = mg – ma The reading on the weighing scale is equal the weight of the girl The reading on the weighing scale is larger The reading on the weighing scale is smaller 3. A boy of mass 50 kg is inside a lift. (a) Sketch the free body diagram using the symbol W and R (c) Calculate the magnitude of the normal reaction force, R when the lift is: (i) stationary (ii) moving upward with an acceleration of 2 ms-2 [g = 9.81 ms-2 ] (iii) move downwards with an acceleration of 1.5 ms-1 . C. Object is pulled by a pulley Calculate resultant force, F Finding the moving mass, m Calculate acceleration, a Calculate tension of the string, T

4. Diagram shows a trolley of mass 2.0 kg being pulled on a table by a load through a pulley. The trolley moves with an acclerattion of 5.0 ms-2 against a friction of 4.0 N. (a) Sketch the free body diagram of the trolley and the load. Use W = the weight of the trolley, R = normal reaction force on the trolley, G = friction, T = tension of the string and B = weight of the load. (b) Compare the weight of the trolley, W with normal reaction force, N (c) calculate the resultant force acting on the trolley, F (d) Calculate the tension in the string pulling the trolley, T (e) What is the mass of the load, m? [gravitational acceleration, g = 9.81 ms-2 ] Tutorial 1.1 1. The figure shows two forces acting at right angles to each other. Which of the following is the resultant force? 2. F1, F2, dan F3 are forces with the same magnitude acting on a wooden block. Which diagram shows the maximum resultant force acting on the wooden block? 3. Diagram shows a boy pulling a block on a rough surface with force, F. Which diagram shows the actions of forces on the block? 4. Diagram shows a car on tow.

Which of the following vector diagram represents the resultant force, F, which acts on the car? PAPER 2 SECTION A 1. Two forces of magnitudes 3 N and 4 N acted on an object Y. The object Y is placed on a smooth horizontal surface. (a) By drawing a scaled parallelogram of forces to determine the resultant force on the object Y. ……………………………………………………….. (b) If the mass of object Y is 2.0 kg, calculate its acceleration (c) State the direction and magnitude of a force that has to be applied on the object Y so that the object is in equilibrium. ……………………………………………………………… 2. Figure shows a lady is riding along a road at a constant velocity. The total of downward force acting on the bicycle and the cyclist is 650 N. The normal reaction of the front tyre is 300 N and forward thrust is 200 N. (a) Calculate the normal reaction ,P acting on the rear tyre . (b) Give one reason why the total resistance, Q should be 200 N at that moment? ……………………………………………………………… (c) What will happen when the forward thrust is increased? ……………………………………………………………… (d) Why the lady thrown forward when the bicycle runs over a stone.? ……………………………………………………………… (e) Explain why the lady can gets serious injuries if she falls into the road which the surface is very hard. ……………………………………………………………… 3. A student studies the effect of the movement of a lift on the readings of a weighing scale. The mass of the student is 50 kg. In this study, the student stands on a weighing scale in a lift as show in the following figure. He records the readings of the weighing scale when the lift is at rest, moving up with acceleration, moving up with uniform velocity, moving down with uniform velocity and moving down with deceleration. The readings of the weighing scale in the study are shown in the following table.

Movement of the lift Reading of the weighing scale/ kg At rest 50 Moving up with acceleration 60 Moving up with uniform velocity 50 Moving down with uniform velocity 50 Moving down with deceleration 60 (a) The mass of the student is 50 kg. What is the weight of the student in newtons? ………………………………. N (b) State two types of movement of the lift when the reading on the weighing scale is equal to the mass of the student. 1.…………………………………………… 2…………………………………………… (c) F is the resultant force that acts on the student. R is the normal reaction of the weighing scale on the student. m is the mass of the student. g is gravitational acceleration. Write a general equation to show the relationship between F, R, m and g. …………………………………………………………… (d) When the lift moves up with acceleration, the normal reaction is greater than his weight. Explain why? …………………………………………………………… (e) (i) What is observed on the reading of the weighing scale when the lift moves down with an acceleration? ……………………………………………………………… (ii) Give a reason for your answer in (e)(i). ……………………………………………………………