Answer Happy

using -
weight of sled 780 kg
travelling at 15 m s
a. Calculate the impulse of the sled's crash in the film. b. What is the average force applied to the sled during the impact?
Only the acceleration is measured during the test, and this is shown in Figure 9.3a. Other quantities such as velocity and displacement can be derived from this data. Deceleration (g) 40- 30 20 10 0 0.02 0.04 0.06 0.08 0.10 Time (s) Figure 9.3a The filtered acceleration data from the sled impact The conservation of energy is shown by the kinetic energy of the sled being dissipated, and this can be seen in the velocity trace as kinetic energy is directly proportional to the square of the velocity. The velocity data, which is calculated by integrating the acceleration data, is shown in Figure 9.3b.
Velocity (ms) 15 10 5 0.02 0.04 0.06 0.08 0.10 Time (s) Figure 9.3b The velocity data calculated from the filtered acceleration data for the sled impact Kinetic energy is converted into other types of energy by permanent deformation of the impact tubes, heating of these tubes, sound energy and a relatively small amount of kinetic energy shown by the sled rolling backwards after the collision due to the elastic portion of the loading of the tubes. This roll back can be seen as both a negative value in the velocity data and the decrease from the peak in the displacement data in Figure 9.3c, which is calculated by integrating the velocity data.
Displacement (m) 0.40- 0.35- 0.30 0.25 0.20 0.15 0.10 0.05 0- 0 0.02 0.04 0.06 0.08 0.10 Time (s) Figure 9.3c The displacement data calculated from the filtered acceleration data for the sled impact This test is an example of an almost perfectly inelastic collision, but it shows that, practice, a completely inelastic collision is very hard to achieve. One of the interesting aspects about this collision is that, looking at the data trace, it exhibits almost constant deceleration during the collision.