Transcript Day 4
Day 4 HW Problem 4-33 • In a game of basketball, a forward makes a bounce pass to the center. The ball is thrown with an initial speed of 4.3 m/s at and angle of 15o below the horizontal. It is released 0.80 m above the floor. • ? What horizontal distance does the ball cover before bouncing ? HW Problem 4-40 • Handball – you hit the ball essentially at ground level and send it toward the all with a speed of 18 m/s at angle of 32o above the horizontal. • ? How long does it take for the ball to reach the wall is it is 3.8 m away? • ? How high is the ball when it hits the wall? Pumkin Chunkin, HW Problem 4-45 • Pumpkins have been projected a distance of 4086 feet in this contest. • ? What is the minimum initial speed needed for such a shot ? • See equation 4-12 HW Problem 4-63 • A racket ball is struck in such a way that it leave the racket with a speed of 4.87 m/s in the horizontal direction. When the ball hits the court, it is a horizontal distance of 1.95 m from the racket. Find the height of the ball when it left the racket. HW Problem 4-91 • Rover bounces on Mars. Just after first bounce, the speed of the Rover is 9.92 m/s at an angle of 75o above the horizontal. The acceleration of gravity, “g”, on Mars is 3.72 m/s2. • ? What is the maximum height of a Rover between its first and second bounce ? HW Problem 5-8 • A 42.0–kg parachutist is moving straight downward with a speed of 3.85 m/s. • ? (a) If the parachutist comes to rest with constant acceleration over a distance of 0.750 m, what force does the ground exert on her ? • ? (b) If the parachutist comes to rest over a shorter distance, is the force exerted by the ground greater than, less than, or the same as in part (a) ? Explain HW Problem 5-18 • On vacation, your 1400-kg car pulls a 560-kg trailer away from a stoplight with an acceleration of 1.85 m/s2. • ? (a) What is the net force exerted on the trailer ? • ? (b) What force does the trailer exert on the car ? • ? (c) What is the net force acting on the car ? HW Problem 5-28 • Two crewmen pull a raft through a lock. One crewman pulls with a force of 130 N at and angle of 34o relative to the forward direction of the raft. The second crewman, on the opposite side of the lock, pulls at an angle of 45o. • ? With what force should be second crewman pull so that the net force of the two crewmen is in the forward direction ? HW Problem 5-30 • To give a 19-kg child a ride, two teenagers pull on a 3.7-kg sled with ropes. Both teenagers pull with a force of 55 N at an angle of 35o relative to the forward direction, which is the direction of motion. The snow exerts a retarding force with a magnitude of 57 N on the sled. • ? Find the acceleration of the sled and the child ? HW Problem 5-40 • You stand on a bathroom scale in an elevator. Though your normal weight is 610 N, the scale at the moment reads 730 N. • ? (a) Is the acceleration of the elevator upward, downward, or zero? • ? (b) Calculate the magnitude of the elevator’s acceleration ? • ? (c) What can you say about the velocity of the elevator ? HW Problem 5-49 • ? (a) Find the normal force exerted on a 2.9-kg book resting on a surface inclined at 36o above the horizontal. ? • ? (b) If the angle of the incline is reduced, do you expect the normal force to increase, decrease, or stay the same ? ? Explain! ? HW Problem 5-64 • On an aircraft carrier, a jet can be catapulted from 0 to 155 mi/hr in 2.0 s. • ? If the average force exerted by the catapult is 9.35 x 105 N, what is the mass of the jet ? HW Problem 5-70 • Your groceries are in a bag with paper handles. The handles will tear of if a force greater than 51.5 N is applied to them. • ? What is the greatest mass of groceries that can be lifted safely with this bag, given that the bag is raised (a) with constant speed, or (b) with an acceleration of 1.25 m/s2 ?