3. TopicSlidesMinutes 1 Displacement 927 2 Vectors 1339 3 Kinematics 1339 4 Graphs 1030 5 Energy 1030 6 Power 515 7 412 8 Shadows 39 9 Field of Vision 721 10 Colors 39 11 Concave mirrors 721 12 Convex mirrors 412 13 Refraction 515 14 Lenses 1030 15 Optical Power 618 Springs

4. Click As illustrated below, the distance a spring is stretched is called the “elongation”. Robert Hooke was the first to discover that the spring force is directly proportional to the elongation. Today, we call this law Hooke’s Law. Where: F S = the spring force (N) k = the spring constant (N/m) x = the elongation (m) The formula for the spring is:F S = kx  (Hooke’s Law)

5. Click When the spring force (F S ) 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.

7. When the spring force is plotted versus the elongation of the spring: Click a)How do you determine the spring constant (k) from the graph? b)How do you determine the potential energy (E P ) stored in a spring from the graph? By finding the slope of the plotted line. By finding the area under the slope. Click Springs Slide: 7. 17. 1

8. The graph on the right represents the force-compression graph of an ideal spring. Click Determine the spring constant. Click Springs Slide: 7. 27. 2

9. 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. Click 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 Springs Slide: 7. 37. 3

10. 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). Determine the frictional force between the surface and the cart as the cart was stretched. Step-1 Find the spring constant (k) Step-2 Calculate the spring force Note that to find the spring constant, we need to invert the slope from the given graph because k = F/x. Step-3 Find the frictional force (f) Click Given Springs Slide: 7. 47. 4

11. 7. 17. 1

12. … and good luck!