1. Page 81 (Ch. 5.4-5.5) 6. The bowling ball moves without acceleration because there is no net force on the ball (neglecting friction) 7.Neglecting air resistance, the horizontal component of velocity for a projectile remains constant due to its inertia. The vertical component is accelerated due to gravity. 8.The downward component of motion of projectile is the same as free fall, since they are both under the influence of gravity. 27. Not at all! Although both inertial horizontal motion and vertical accelerated motion combine to form a curved, parabolic path, neither depends on the other.

2. Additional Questions B 1.A projectile is an object that moves through the air under the influence of gravity. 2.The curved path of a projectile is a result of the combination of horizontal motion at a constant velocity and vertical motion that is accelerated at 9.8 m/s 2

3. Additional Questions II B 3.5.8 a represents horizontal motion at a constant velocity and 5.8 b demonstrates vertical motion that is acceleration. 4.Same: both fall at the same rate. Different is that the yellow ball is also moving horizontally while the red ball falls straight down. 5.Parabola is the curved shape of a projectile’s path, and trajectory is the path taken by the projectile.

4. Additional Questions III. A) Pg. 99-100 13. Freefall occurs when an object is falling and only experiences the force of gravity. 15. Greater mass means proportionally greater weight, and proportionally more force. The force (or weight) to mass ratio always produces the same rate of acceleration. Since there is no air resistance in freefall, the difference in weights (or masses) does not change acceleration.

5. Additional Questions, pg. 100) 16. Air resistance acting on an object increases with increasing speed. 17. The object at the greater speed encounters more air resistance. 18. The acceleration equals zero at terminal velocity because the weight of the falling object is balanced by air resistance, so the net force equals zero. 19. Air resistance is also affected by surface area (the greater the surface area, the greater the air resistance). 20. 100-N of weight is balanced by 100-N of air resistance at terminal velocity.

6. Additional Questions III b) 1. Net force equals the weight of the object. 2. Air resistance is dependent upon the object’s surface area and speed. 3. Air resistance can be reduced by improving the aerodynamics (stream lining) or by lessening the surface area. It would also be possible by applying brakes to a car to reduce speed.

7. Additional Questions III b) 4. The elephant experiences the greater air resistance, because the elephant has a greater surface area, and would be falling faster than the paper. Note: the rate of acceleration and the net force acting on the two objects are directly related. More net force means more acceleration, which means that the object can increase in speed. It does not take much air resistance to balance the weight of the paper, but it will take a great deal of air resistance to balance the weight of the elephant (to reach equilibrium). Thus, the elephant must be falling at large rate of speed to reach terminal velocity.

8. Additional Questions III b) 5. Terminal speed (or velocity) is the maximum falling speed an object can reach. 6. Air resistance and weight are balanced at terminal velocity. 7. terminal velocity (35 N of Fg balanced by 35 N of Fair); free fall (only 35 N of Fg) 8. A feather has very little weight and a surface area that is much greater than its width. It does not take much air resistance to balance the weight of the feather, so it reached terminal velocity quickly at a low rate of speed. 9. Zero acceleration means that the object is moving at a constant velocity; zero velocity means the object is at rest.