166 1. A weightlifter uses a force of 375 N to lift weights directly upward through a distance of 0.85 m. Determine the work done on the weights by the weightlifter. 2. A tow truck uses a winch with a rope attached to pull a car that is stuck in ditch. The rope exerts a force of 9.9 X 103 N on the car body, and the angle between the rope and the direction the car moves is 12. Determine the amount of work done on the car by the tow truck to move the car 4.3 m. 169 3. A hiker pulls a sled a distance of 223 m with a constant force of 122 N exerted at an angle of 37. Friction acts on the sled with a constant force of 72.3 N. Calculate the work done on the led by the hiker and by friction, and the total work done on the sled. 4. A 2.5 kg piece of wood falls onto a carpenter's table from a height of 2.0 m above the table. T a) Calculate the kinetic energy of the wood as it hits the table. (b) Calculate the speed of the wood as it hits the table. 5. Calculate the gravitational potential energy relative to the ground of a 5.0 kg Canada goose flying at a height of 553 m above the ground. 6. A bicycle and rider have a combined mass of 79.3 kg and a momentum of 2.16 x 103 kg.m/s [W]. Determine the velocity of the bicycle. K/U-227 7. A soccer player kicks a 0.43 kg soccer ball down a smooth (frictionless) hill 18 m high with an initial speed of 7.4 m/s (Figure 5).187 (a) Calculate the ball's speed as it reaches the bottom of the hill. b) The soccer player stands at the same point on the hill and gives the V= 7.4 m/s ball a kick up the hill at 4.2 m/s. The ball moves up the hill, comes to rest, and rolls back down the hill. Determine the ball's speed as it Ay = 18 m reaches the bottom of the hill. Figure 5 8. You accidentally drop a cellphone, which has a mass of 225 g, from a height of 74 cm. TMA 227 (a) Calculate the cellphone's momentum at the moment of impact with the sidewalk. (b) If the cellphone lands on a grassy lawn, is its momentum less, the same, or greater? Explain your answer. Two balls collide a perfectly elastic collision. Ball has mass 3.5 kg and is initially travelling at velocity of 5.4 m/s [right]. collides head-on with stationary ball 2 with mass 4.8 kg. Determine the final velocity of ball 2. ---236 10. A ball of mass 80.0 g is moving at 7.0 m/s [W] when it undergoes a head-on elastic collision with a stationary ball of mass 60.0 g. Assume the collision is one-dimensional. Calculate the velocity of each ball after the collision. 243