Topic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Displacement Vectors Kinematics Graphs Energy Power Springs Shadows Field of Vision Colors Concave mirrors Convex mirrors Refraction Lenses Optical Power Slides Minutes 9 27 13 39 13 39 10 30 10 30 5 15 4 12 3 9 7 21 3 9 7 21 4 12 5 15 10 30 6 18 As illustrated below, the distance a spring is stretched is called the вЂњelongationвЂќ. Robert Hooke was the first to discover that the spring force is directly proportional to the elongation. Today, we call this law HookeвЂ™s Law. The formula for the spring is: FS = kx пЃ… (HookeвЂ™s Law) Where: FS = the spring force (N) k = the spring constant (N/m) x = the elongation (m) Click When the spring force (FS) is plotted versus the elongation (x) of the spring, the resulting graph is a linear relation. The slope of the curve represents the spring constant while the area under the curve represents the potential energy stored in the spring. Click Springs Slide: 7. 1 When the spring force is plotted versus the elongation of the spring: a) How do you determine the spring constant (k) from the graph? By finding the slope of the plotted line. b) How do you determine the potential energy (EP) stored in a spring from the graph? By finding the area under the slope. Click Springs Slide: 7. 2 The graph on the right represents the force-compression graph of an ideal spring. Determine the spring constant. Click Springs Slide: 7. 3 Jim wants to compress a coil whose spring constant is 120 N/m. To do so, he uses a lever attached in such a way that the actual mechanical advantage (AMA) is 3 as illustrated below. How much force must Jim apply in order to compress the spring a distance of 50 cm? Note that the resistance force = the spring force Click Springs Slide: 7. 4 The graph on the right was obtained by applying various weights to a spring. The spring is then attached to a 5.0 kg cart and stretched 0.40 m by an applied force of 25 N (as illustrated). Note that to find the spring constant, 0.40 m Determine the frictional force between we need to invert the slope from the the surface and the cart as the cart given graph because k = F/x. FA = 25 was stretched. N 5.0 kg Step-1 Find the spring constant (k) Step-3 Find the frictional force (f) Step-2 Calculate the spring force Given Click Springs Slide: 7. 1 вЂ¦ and good luck!