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Physics 141 Worksheet Chapter 7 due Wed 5/18 00 Summer 2022 Name: Box: 1. Write an equation representing work that involves the force, F, the displacement, Ax, and the angle between the two, 0. 2. A 55 kg packing crate is pulled with constant speed across a rough floor with a rope that is at an angle of 40 degrees above the horizontal (A) Sketch a free-body diagram of the crate. (B) If the tension in the rope is 125 N, how much work is done by the rope on the crate to move it 5.0 m (use the answer to question (1))? (B) What is the net work done on the crate? (Note the constant speed to get the simplest number in the universe) Wet= 3 (C) How much work is done by friction? 2. Write an equation representing kinetic energy. 3. A 9.5 g bullet has a speed of 1.30 km/s. (a) What is its kinetic energy? (b) How many times larger is the kinetic energy if the speed is doubled? J X larger 4. The work - kinetic energy theorem states that the net work done on an object equals the in kinetic energy. 5. A 50 kg biker rides his 10 kg bike with a speed of 10 m/s. (a) Use the work-kinetic energy theorem to calculate the work done by the brakes to make him stop (is the work positive or negative?). W- J (b) If he stops in 5 meters, what was the average stopping force? R 6. A 55 kg skateboarder enters a ramp moving horizontally with a speed of 6.5 m/s, and leaves the ramp moving vertically with a speed of 4.1 m/s. Find the height of the ramp. (a) Draw lines to match the expressions for the initial and final potential and kinetic energies. 1/2mv? PE₁ 0 ΚΕ PE 1/2mv² mgh KE