G9IG Physics Worksheet 03 PDF

Topic: Forces Subject: Physics Class: G9IG Worksheet 03 1. Two students make the statements about acceleration that are given below. Student A: For a given mass the acceleration of an object is proportional to the resultant force...

Topic: Forces Subject: Physics Class: G9IG Worksheet 03 1. Two students make the statements about acceleration that are given below. Student A: For a given mass the acceleration of an object is proportional to the resultant force applied to the object. Student B: For a given force the acceleration of an object is proportional to the mass of the object. a. One statement is correct and one is incorrect. Re-write the incorrect statement, making changes so that it is now correct. For a given........................ the acceleration of an object is................................................................................................................................................................................................................................................... b. State the equation which links acceleration a, resultant force F and mass m. c. Describe what happens to the motion of a moving object when there is no resultant force acting on it............................................................................................................................. d. A resultant force is applied to it in the opposite direction to the motion............................................................................................................................. Page 1 of 10 2. A uniform metre rule is pivoted at its centre, which is also the position of its centre of mass. Three loads, 2.0 N, F and 3.0 N are positioned on the rule at the 20 cm, 30 cm and 90 cm marks respectively, as shown in Figure below. a. Calculate the moment of the 3.0 N load about the pivot. moment =.............................................. b. Calculate the moment of the 2.0 N load about the pivot. moment =............................................... c. The force F maintains the metre rule in equilibrium on the pivot. Calculate the value of F. F =......................................................... Page 2 of 10 3. A uniform metre rule has a weight of 1.2 N and can be considered to act at its 50 cm mark. The pivot is positioned under the 30 cm mark and the 2.0 N load is placed on the rule as shown in the figure below. The position of the 2.0 N load is adjusted until the metre rule is again in equilibrium. Determine the position of the 2.0 N load. 2.0 N load is at the.......................................... cm mark 4. a. A loose uniform wooden floorboard weighs 160 N and rests symmetrically on four supports P, Q, R and S. The supports are 0.50 m apart, as shown in the figure below. Page 3 of 10 Calculate the force exerted on the floorboard by each of the supports, and state the direction of these forces. One value is already given for you. force exerted by P =................................................... force exerted by Q =................. 40 N......................... force exerted by R =................................................... force exerted by S =................................................... direction =.................................................... b. A workman of weight W stands on the end of the floorboard described in (a). This just causes the floorboard to tip up, as shown in the figure below. The supports are each 0.060 m thick. Calculate the weight W of the workman. Weight W = …………………………………… Page 4 of 10 5. A student investigated the stretching of a spring by hanging various weights from it and measuring the corresponding extensions. The results are shown below. On the figure below, plot the points from these results. Do not draw a line through the points yet. a. The student appears to have made an error in recording one of the results. Which result is this?.............................................................................................................................. Page 5 of 10 b. Ignoring the incorrect result, draw the best straight line through the remaining points. c. State and explain whether this spring is obeying Hooke’s Law......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... d. The student estimates that if he hangs a 45 N load on the spring, the extension will be 920 mm. Explain why this estimate may be unrealistic............................................................................................................................................................................................................................................................................................................................................................................. 6. A force acting on an object causes the object to accelerate. In which direction is the acceleration?...................................................................................................... 7. A woman of mass 60 kg is standing in a lift at a shopping centre. The lift is at rest. a. State the value of the weight of the woman. Weight =................................................. b. State the value of the force exerted on the woman by the floor of the lift........................................................................................................................... Page 6 of 10 c. Calculate the force required to accelerate the woman at 2.5 m/s2. Force = ……………………………. 8. The figure below shows part of the extension-load graph for a spring. The spring obeys Hooke’s law between points A and B. a. On the above figure, complete the graph between A and B. b. State the name of point B........................................................................................................................... c. The spring has an unstretched length of 4.0 cm. An object is hung on the spring and the spring length increases from 4.0 cm to 6.0 cm. Calculate the mass of the object. mass =........................................... Page 7 of 10 9. The figure below shows the extension-load graph for a spring. Point P is the limit of proportionality. a. Name the law obeyed by the spring from the origin to P........................................................................................................................... b. Describe two features of the graph which show that the law is obeyed. 1........................................................................................................................ 2........................................................................................................................ c. On the above figure, sketch a possible continuation of the graph when the spring is loaded beyond the limit of proportionality. 10. a. State Hooke’s law. …………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………… Page 8 of 10 b. The figure below shows a graph of the stretching force F acting on a spring against the extension x of the spring. i. State the features of the graph that show that the spring obeys Hooke’s law..................................................................................................................................................................................................................................................... ii. Calculate k, the force per unit extension of the spring. k =................................................. Page 9 of 10 c. The limit of proportionality of the spring is reached at an extension of 50 mm. Continue the graph in the above figure to suggest how the spring behaves when the stretching force is increased to values above 125 N. d. Another spring has a smaller value of k. This spring obeys Hooke’s law for extensions up to 80 mm. On the grid of the figure, draw a possible line of the variation of F with x for this spring. Page 10 of 10