A 19.7 kg block is dragged…

Physics Questions

A 19.7 kg block is dragged over a rough, horizontal surface by a constant force of 188 N acting at an angle of 28.6 degrees above the horizontal. The block is displaced 48.7 m, and the coefficient of kinetic friction is 0.103. Find the work done by the 188 N force in joules (J). Additionally, determine the magnitude of the work done by the force of friction in joules (J). What is the change in kinetic energy of the crate in joules (J)? Lastly, what is the speed of the crate after it is pulled the 48.7 m in meters per second (m/s)?

Answer

This problem involves work, energy conservation, friction, normal force, and kinetic energy principles. a) The work done by the applied force (188 N) is calculated as follows: W = Fd CosŒ∏, where W = ? (work done), F = 188 N (applied force), d = 48.7 m (distance), and Œ∏ = 28.6¬∞ (angle). Consequently, W = (188 N)(48.7 m) Cos 28.6¬∞ = 8038.46 J. b) The work done against friction can be derived from the equilibrium in the vertical direction: N + FSinŒ∏ = weight of the block (mg). Here, the weight is 19.7 kg x 9.81 m/s¬≤ = 193.26 N. Solving for the normal force, we find N = 103.26 N. The frictional force is then calculated as f = ŒºN, leading to f = (0.103)(103.26 N) = 10.64 N. The work done by friction is W_f = fd = (10.64 N)(48.7 m) = 517.96 J. c) The change in kinetic energy using conservation of energy principle is ŒîKE = W – W_f = 8038.46 J – 517.96 J = 7520.5 J. d) The final speed is determined with ŒîKE = 7520.5 J. Using the formula 1/2 m(v_f¬≤ – v_i¬≤), where mass m = 19.7 kg and initial speed v_i = 0 m/s, we find v_f¬≤ = (2 x 7520.5 J) / 19.7 kg, resulting in v_f = ,(763.5 m¬≤/s¬≤) = 27.63 m/s.

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