9:53 076_Mome... Momentum Practice Problems (from Giancoli Textbook) 7. (II) A child in a boat throws a 5.30-kg package out horizon- tally with a speed of 10.0 m/s, Fig. 7-31. Calculate the velocity of the boat immediately after, assuming it was initially at rest. The mass of the child is 24.0 kg and the mass of the boat is 35.0 kg. 11. (II) A 22-g bullet traveling 240 m/s penetrates a 2.0-kg block of wood and emerges going 150 m/s. If the block is stationary on a frictionless surface when hit, how fast does it move after the bullet emerges? 13. (III) Air in a 120-km/h wind strikes head-on the face of a building 45 m wide by 75 m high and is brought to rest. If air has a mass of 1.3 kg per cubic meter, determine the average force of the wind on the building. 16. (II) A golf ball of mass 0.045 kg is hit off the tee at a speed of 38 m/s. The golf club was in contact with the ball for 3.5 x 103 s. Find (a) the impulse imparted to the golf ball, and (b) the average force exerted on the ball by the golf club. 24. (III) (a) Calculate the impulse experienced when a 55-kg person lands on firm ground after jumping from a height of 2.8 m. (b) Estimate the average force exerted on the person's feet by the ground if the landing is stiff-legged, and again (c) with bent legs. With stiff legs, assume the body moves 1.0 cm during impact, and when the legs are bent, about 50 cm. [Hint: The average net force on him, which is related to impulse, is the vector sum of gravity and the force exerted by the ground. See Fig. 7-34.] We will see in Chapter 9 that the force in (b) exceeds the ultimate strength of bone (Table 9-2). mg grd FIGURE 7-34 Problem 24. 51. (II) The CM of an empty 1250-kg car is 2.40 m behind the front of the car. How far from the front of the car will the CM be when two people sit in the front seat 2.80 m from the front of the car, and three people sit in the back seat 3.90 m from the front? Assume that each person has a mass of 65.0 kg. 63. (II) A 52-kg woman and a 72-kg man stand 10.0 m apart on nearly frictionless ice. (a) How far from the woman is their CM? (b) If each holds one end of a rope, and the man pulls on the rope so that he moves 2.5 m, how far from the woman will he be now? (c) How far will the man have moved when he collides with the woman? 66. (III) A huge balloon and its gondola, of mass M, are in the air and stationary with respect to the ground. A passenger, of mass m, then climbs out and slides down a rope with speed v, measured with respect to the balloon. With what speed and direction (relative to Earth) does the balloon then move? What happens if the passenger stops? An explosive cannon ball is launched at an initial speed of v at an angle above the ground. The cannon was aimed correctly to hit a target a distance R away. a) Determine the speed of the half of the cannon ball which is flung forward. b) When the ball was half-way through its flight, it exploded prematurely into two identical halves. One half was thrown backwards, landing exactly on the cannon which fired it. How far away (in terms of R) did the other half land from its original target. c) Justify that your answer for part (b) is true no matter where in the flight of the cannon ball the explosion occurred.