Projectile Motion

Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance? (There could be more than one correct choice) A. The acceleration of the object is zero at its highest point B. The acceleration of the object is +g when the object is rising and -g when it is falling C. The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward D. The speed of the object is zero at its highest point E. The speed of the object is constant but its velocity is not constant

C

Which projectile spends more time in the air, the one fired from 30∘ or the one fired from 60∘? A. The one fired from 30∘ B. They both spend the same amount of time in the air. C. The one fired from 60∘

C

image 1: https://session.masteringphysics.com/problemAsset/1872400/3/q3-22.jpg Which vector best represents the ball's velocity at position 3? A B C D E

C

image 2: https://session.masteringphysics.com/problemAsset/1780547/32/pre_vid_500px.jpg How does the vertical acceleration at point A compare to the vertical acceleration at point C? A. Both accelerations are equal to zero. B. The acceleration at A is less than that at C. C. Both accelerations are equal to free fall acceleration. D. The acceleration at A is greater than that at C.

C

image 2: https://session.masteringphysics.com/problemAsset/1780547/32/pre_vid_500px.jpg Is the vertical component of velocity ever zero? If so, where? A. Yes, it is zero at points A and E. B. Yes, it is zero at all points. C. Yes, it is zero at point C. D. No, it is never zero.

C

image 2: https://session.masteringphysics.com/problemAsset/1780547/32/pre_vid_500px.jpg How does the magnitude of the horizontal velocity change as the human cannonball passes through points A, B, C, D, and E? A. It decreases. B. It increases. C. It decreases then increases. D. It does not change.

D

For general projectile motion with no air resistance, the horizontal component of a projectile's acceleration A. remains a non-zero constant B. continuously decreases C. continuously increases D. first decreases and then increases E. is always zero

E

For general projectile motion with no air resistance, the horizontal component of a projectile's velocity A. remains a non-zero constant B. continuously decreases C. continuously increases D. first decreases and then increases E. remains zero

A

For general projectile motion with no air resistance, the vertical component of a projectile's acceleration A. remains a non-zero constant B. continuously decreases C. continuously increases D. first decreases and then increases E. is always zero

A

In an air-free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height. Compare the times of fall of the two pebbles. A. They hit at the same time B. The thrown pebble hits first C. The dropped pebble hits first D. We cannot tell without knowing which pebble is heavier

A

image 1: https://session.masteringphysics.com/problemAsset/1872400/3/q3-22.jpg Which vector best represents the ball's acceleration at position 2? A B C D E

A

image 1: https://session.masteringphysics.com/problemAsset/1872400/3/q3-22.jpg Which vector best represents the ball's acceleration at position 3? A B C D E

A

Which ball (if either) has the greatest speed at the moment of impact? A. The dropped ball B. The ball thrown horizontally C. Both balls have the same speed.

B

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically. Which object is traveling faster when it hits the level ground below if neither of them experiences any air resistance? A. It is impossible to tell because we do not know their masses B. the ball C. the stone D. Both are traveling at the same speed

B

A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will A. depend on the speed of the plane when the package was released B. be directly over the package C. be behind the package D. be in front of the package

B

Consider the video demonstration that you just watched. A more complete explanation of what you saw will be possible after covering Newton's laws. For now, consider the following question: How would the result of this experiment change if we replaced the ball with another one that had half the mass? Ignore air resistance. A. The ball would land behind the cart. B. The ball would still land in the cart. C. The ball would land ahead of the cart.

B

A rock is thrown from the upper edge of a tall cliff at some angle above the horizontal. It reaches its highest point and starts falling down. Which of the following statements about the rock's motion are true just before it hits the ground? (There could be more than one correct choice.) A. Its horizontal velocity component is the same as it was just as it was launched. B. Its velocity is vertical. C. Its speed is the same as it was just as it was launched. D. Its horizontal velocity component is zero. E. Its vertical velocity component is the same as it was just as it was launched.

A

You toss a basketball toward the basket. At the highest point of its arc, A. The vertical component of the velocity is zero. B. The horizontal component of the velocity is zero. C. Both the horizontal and vertical components of the velocity are zero.

A

image 2: https://session.masteringphysics.com/problemAsset/1780547/32/pre_vid_500px.jpg When launched, the human cannonball's initial velocity has a positive x-component and a positive y-component. Rank the vertical velocity components at points A through E from most positive to most negative.

A B C D E

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. If there is no air resistance, when they reach the lake below A. the splashdown speed of James must be 9.8 m/s larger than that of John. B. the splashdown speed of John is larger than that of James. C. the splashdown speed of James is larger than that of John. D. they will both have the same splashdown speed. E. the splashdown speed of John must be 25 m/s larger than that of James.

B

The crew of a cargo plane wishes to drop a crate of supplies on a target below. To hit the target, when should the crew drop the crate? Ignore air resistance. A. After the plane has flown over the target B. Before the plane is directly over the target C. When the plane is directly over the target

B

Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30° above the horizontal. Which of the following statements are true about just as the snowballs reach the ground below? (There could be more than one correct choice.) A. Both snowballs hit the ground at the same time. B. Mary's snowball reaches the ground before Debra's snowball. C. Mary's snowball will have a higher speed than Debra's snowball. D. Both snowballs will hit the ground with the same speed. E. Debra's snowball will have a higher speed than Mary's snowball.

B&D

Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30° above the horizontal. Which of the following statements are true about just before the snowballs reach the ground below? (There could be more than one correct choice.) A. Mary's snowball will stay in the air longer than Debra's snowball. B. Debra's snowball will stay in the air longer than Mary's snowball. C. Both snowballs will take the same amount of time to hit the ground. D. Debra's snowball has exactly the same acceleration as Mary's snowball. E. Mary's snowball has a greater downward acceleration than Debra's snowball.

B&D

Consider the video you just watched. Suppose we replace the original launcher with one that fires the ball upward at twice the speed. We make no other changes. How far behind the cart will the ball land, compared to the distance in the original experiment? A. half as far B. twice as far C. four times as far D. the same distance E. by a factor not listed above

C

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. Compare the time it takes each to reach the lake below if there is no air resistance. A. John reaches the surface of the lake first. B. Cannot be determined without knowing the mass of both James and John. C. James reaches the surface of the lake first. D. James and John will reach the surface of the lake at the same time. E. Cannot be determined without knowing the weight of both James and John.

D

image 1: https://session.masteringphysics.com/problemAsset/1872400/3/q3-22.jpg Which vector best represents the ball's velocity at position 2? A B C D E

D

A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory A. both the velocity and the acceleration of the soccer ball are zero. B. the ball's acceleration points upward. C. the ball's velocity points downward. D. the ball's acceleration is zero but its velocity is not zero. E. neither the ball's velocity nor its acceleration are zero.

E

true or false: A boulder rolls off of a very high cliff and experiences no significant air resistance. While it is falling, its trajectory is never truly vertical.

true