Physics 213 Test 3 10 Points Each November 12, 1997

1. A 30 kg boy coasts east on a 20 kg cart at a speed of 4.0 m/s. The boy pushes off the cart which flies east at 13.0 m/s relative to the ground. Determine the speed of the boy immediately after he pushes off.

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6. Use the coordinate axes at right to find the sum of the 4 forces in the left diagram.

9. Three carts of masses 4 kg, 10 kg, and 3 kg move on a frictionless track with speeds of 5 m/s, 3 m/s, and 4 m/s , as shown in the figure below. The carts stick together after colliding. What is the final velocity of the three carts after all collisions have taken place?

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A 70 kg student is hanging from a 150 kg helium balloon (including basket and mass of helium). The balloon is rising at a constant speed of 8 m/s. The "lift" on the balloon due to the buoyant force is constant. The student begins to climb up the rope at a speed of 15 m/s as measured from the balloon. The balloon's upward speed is decreased as the student climbs.

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