Physics- Chapter 3

A ball rolling rapidly along a tabletop rolls off the edge and falls to the floor. At the exact instant that the first ball rolls off the edge, a second ball is dropped from the same height. Which ball, if either, reaches the floor first? Explain. a. The rolling ball reaches the floor first because it has an initial velocity and the dropped ball does not. b. The dropped ball reaches the floor first because its velocity is only in the y-direction. c. Both balls reach the floor at the same time because they both have the same initial zero y-component of velocity.

c. Both balls reach the floor at the same time because they both have the same initial zero y-component of velocity.

A steel ball is dropped from a diving platform (with an initial velocity of zero). Use the approximate value of g = 10 m/s2. (a) What is the velocity of the ball 1.0 seconds after its release? ____ m/s (b) What is its velocity 3.8 seconds after its release? ____ m/s

(a) 10 (b) 38

A ball is thrown upward with an initial velocity of 13 m/s. At what time does the ball reach the high point in its flight? (Use the approximate value of g = 10 m/s2, and remember that the velocity is equal to zero at the high point.) ______ S

1.3

A bullet is fired horizontally with an initial velocity of 700 m/s at a target located 300 m from the rifle. (a) How much time is required for the bullet to reach the target? ______ s (b) Using the approximate value of g = 10 m/s2, how far does the bullet fall in this time? _____ m

(a) 0.429 (b) 0.92

A ball rolls off a platform that is 6 meters above the ground. The ball's horizontal velocity as it leaves the platform is 4.7 m/s. (a) How much time does it take for the ball to hit the ground? (See the example box, use g = 10 m/s2.) 1.09 ____ s (b) How far from the base of the platform does the ball hit the ground? _____ m

(a) 1.09 (b) 5.123

A steel ball is dropped from a diving platform (with an initial velocity of zero). Use the approximate value of g = 10 m/s2. (a) Through what distance does the ball fall in the first 1.5 seconds of its flight? _____ m (b) How far does it fall in the first 4 seconds of its flight? ____ m

(a) 11.25 (b) 80

A ball is thrown upward with an initial velocity of 12 m/s. Using the approximate value of g = 10 m/s2, what are the magnitude and direction of the ball's velocity at the following times? (a) 1.00 s after it is thrown ____ m/s upward or downward (b) 2.10 s after it is thrown _____ m/s

(a) 2 m/s, upward (b) 9, downward

A ball is thrown upward with an initial velocity of 14 m/s. Using the approximate value of g = 10 m/s2, how high above the ground is the ball at the following times? (a) 1.10 s after it is thrown _____ m (b) 1.90 s after it is thrown _____ m

(a) 9.35 (b) 8.55

A lead ball and an aluminum ball, each 1 in. in diameter, are released simultaneously and allowed to fall to the ground. Due to its greater density, the lead ball has a substantially larger mass than the aluminum ball. Which of these balls, if either, has the greater acceleration due to gravity? Explain. a. Both will fall with the same acceleration, regardless of their mass. b. The aluminum ball will fall with greater acceleration because of its small density. c. The lead ball will fall with greater acceleration because of its greater mass.

a. Both will fall with the same acceleration, regardless of their mass.

A rock is dropped from the top of a diving platform into the swimming pool below. Will the distance traveled by the rock in a 0.1-second interval near the top of its flight be the same as the distance covered in a 0.1-second interval just before it hits the water? Explain. a. No, the distance traveled in the 0.1 s just before hitting the water will be greater since the rock's velocity will be greater. b. No, the distance traveled in the first 0.1 s will be greater since the rock's velocity will be smaller. c. Yes, the distance traveled for any 0.1-s interval is the same since the rock's acceleration is constant. d. Yes, the distance traveled in the 0.1 s just before hitting the water will be the same since the rock is a projectile.

a. No, the distance traveled in the 0.1 s just before hitting the water will be greater since the rock's velocity will be greater.

You toss a ball straight up in the air. At the highest point, the ball's: a. velocity is zero and the acceleration is downward. b. velocity is zero and the acceleration is upward. c. acceleration is zero but not its velocity. d. velocity and acceleration are zero.

a. velocity is zero and the acceleration is downward.

In a laboratory on Earth, all the air is pumped from a large tube. A feather and a steel ball are simultaneously released from rest inside the tube. What happens next? a. The steel ball falls and hits the bottom before the feather b. Both objects fall and hit the bottom at the same time c. Both objects float weightless inside the tube d. The feather falls and hits the bottom before the steel ball

b. Both objects fall and hit the bottom at the same time

A cannonball fired at an angle of 70° to the horizontal stays in the air longer than one fired at 45° from the same cannon. Will the 70° shot travel a greater horizontal distance than the 45° shot? Explain. a. Yes, since the cannonball fired at an angle of 70° stays in the air longer it will travel a greater horizontal distance than the cannonball fired at 45°. b. No, the cannonball fired at 70° has a larger vertical component of velocity so will have a higher ascent and will not travel as far horizontally as the cannonball fired at 45°. c. There is not enough information to determine which cannonball will travel a greater horizontal distance.

b. No, the cannonball fired at 70° has a larger vertical component of velocity so will have a higher ascent and will not travel as far horizontally as the cannonball fired at 45°.

A ball thrown straight upward moves initially with a decreasing upward velocity. What are the directions of the velocity and acceleration vectors during this part of the motion? a. The directions of both the velocity vector and the acceleration vector are upward. b. The direction of the velocity vector is downward and the direction of the acceleration vector is upward. c. The direction of the velocity vector is upward and the direction of the acceleration vector is downward. d. The directions of both the velocity vector and the acceleration vector are downward. (b) Does the acceleration also decrease? Explain. a. Yes, the acceleration decreases as the ball is thrown upward. b. No, the acceleration does not decrease but remains constant. c. No, the acceleration increases as the ball is thrown upward.

c. The direction of the velocity vector is upward and the direction of the acceleration vector is downward. (b) b. No, the acceleration does not decrease but remains constant.