(1) m v Ballistic pendulums are used to be used for measuring bullet speeds. Such a pendulum is made by hanging a wooden block with mass M = 0.99 kg with strings of L. = 4.0 m length. You can neglect the thickness of the wood. (1) A bullet with mass m = 0.01 kg is fired with an unknown speed u. (2) The bullet hits the wood and is stuck inside. (3) The wooden block together with the bullet inside then rises to a maximum angle of 8 = 37". I IN M (a) Let u be the speed of the block immediately after the bullet-wood collision (i.e., after bullet stopped relative to the wood). Assume that the collision happened in a negligible time so that the block is still at its lowest position. Find 4 m/s w = 4 Correct answer, well done. (b) Find the speed of the bullet v. 400 m/s = 400 Correct answer, well done. (c) How much energy is last into heat in the bullet-wood collision? Elast-79200 -79200 J X Incorrect answer. (d) When the wooden block is inspected, it is observed that the bullet has been buried d = 10 cm inside. Assuming that a frictional force F, of constant magnitude has stopped the bullet inside the wood, find the magnitude of the frictional force. (Note that d is the relative displacement of bullet and wood during the collision when Facts.) F = 24750 24750 N X Incorrect answer.