B- A1. A box is pushed along the ground from point A to point B along two paths
ID: 2305971 • Letter: B
Question
B- A1. A box is pushed along the ground from point A to point B along two paths shown below (dotted lines solid lines). For which path is work done by the force of gravity greatest? the A2. A box is pushed along the ground from point A to point B along the two paths shown above (dotted lines solid lines). For which path is the work done by friction greatest? A3. One person drops a ball from the top of a building while another person at the bottom observers its motion. Will these people always agree on (a) the value of the gravitational potential energy? (b) on the kinetic energy of the ball at some point in its motion A4. A work? downward? skier slides down a mountain at constant speed, is the the net force on the skier doing A5. Your neighborhood cashier begins to talk to you about physics and she claims "A force that is always perpendicular to the velocity of an object does no work. Do you agree or disagree? Part B B1. A 20 kg box is dragged across the floor for 3 m at a constant speed by a rope with a tension of 25 N. (a) What is the work done by the rope? (b) What is the work done by gravity? 6 points each. B2. An object with mass of 1.5 kg is moving to the left at 10 m/s. An applied force causes it to move to the right at 10 m/s. What is the work done by the applied force? 8 points B3. A popsicle is placed in a microwave. The microwave delivers 200 W to it. If it take 50 kJ of energy to melt it. How much time does it take to melt it? 6 points B4. A 0.3 kg rock is thrown vertically upward from the top of a cliff that is 16 m above the ground. When it hits the ground it has a speed of 22 m/s. Calculate the initial speed of the rock. 8 points. B5. A 700 g block with a spring constant k- 400 N/m is attached to a spring. The block and spring system is compressed a vertical distance of 19.0 cm and held it placed. The block is released and shot up to a height "h" above its rest position. Calculate the height 'h". 10 points Long AnswersExplanation / Answer
B3) Times taken = Work done / Power
= 50000 / 200
= 250 s
B4) KE (at top) +PE = Ke(at bottom)
0.5mv1^2 + mgh = 0.5mv2^2
0.5*v1^2 + 9.8*16 = 0.5*22^2
v1 = 13 m/s
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