RI Y5 Remedial Forces Assignment

Raffles Institution Physics Department Y5 H2 Physics Term 3 Remedial 1 Chapter 4: Forces How do I know it is a Forces question? The question usually contains “at equilibrium”, “at rest”, “held” or “moves/travels horizontally/vertically at a constant speed”. Solving Problems Involving System in Equilibrium 1 Select a body or system of bodies for analysis. 2 Draw a free-body diagram showing all the forces acting on the body or system. Take care to draw the arrows for the forces starting from thei r correct points of action, as these will affect the moment calculation. 3 Select a positive direction each for forces and moments. A wise choice of the point of reference (a.k.a. the pivot) simplifies the calculation for moments tremendously. 4 Evaluate the type of problem to be solved and form the equations using: 0 and 0 and 0xyFF     Hooke’s Law 1 A mass is attached to two springs as shown. The springs A and B have spring constants k and 3k respectively. Forces are applied to the spri ngs such that the free end of A is displaced x to the left and that of B is displaced y to the right, but there is no change in the displacement of the mass. What is the value of y? A 1 3 x B x C 3 2 x D 3 x NYJC/09/I/8 Upthrust 2 An oil tanker, with vertical sides, has an external cross-sectional area of 36 500 m 2 in the plane of the sea. The tanker carries oil of density 930 kg m 3 in its tanks, which have a constant cross-sectional area of 34 000 m2 and depth 22.0 m. Sea water has density 1030 kg m3. By how much does the tanker rise in the water when it unloads its oil? A 26.2 m B 22.7 m C 21.3 m D 18.5 m 2009/I/10 x 3k spring A mass k spring B smooth horizontal plane y

Raffles Institution Physics Department Y5 H2 Physics Term 3 Remedial 2 Worked Example 1 (3 forces acting on a body) A ladder of weight W rests against a vertical wall. Friction between the ladder and the ground and also between the ladder and the wall prevents the ladder from slipping. Which diagram shows the directions of the forces on the ladder? 2008/1/7 3 A uniform rod XY is freely hinged to the wall at X. It is held horizontal by a force F acting from Y at an angle  to the vertical as shown in the diagram. Which arrow shows the direction of the reaction force exerted by the wall on the rod? 4 A man who weighs 600 N is sitting on a chair with his feet on the floor and arms resting on the armrests. The chair weighs 100 N. Each armrest exerts an upward force of 25.0 N on each arm and the seat exerts an upward force of 500 N. What force does the floor exert on his feet? A 50 N B 75 N C 100 N D 150 N SAJC/09/I/5 W x F A D C B  X Y

Raffles Institution Physics Department Y5 H2 Physics