ch. 4 (physics) / 4.1
A bullet is fired from ground level with a speed of 150 m/s at an angle 30.0° above the horizontal at a location where g = 10.0 m/s2. What is the vertical component of its velocity when it is at the highest point of its trajectory?
A) 0 m/s
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°. When the snowballs reach the ground below,
A) Debra's snowball will stay in the air longer than Mary's.
A monkey is sitting at the top of a tree 20 m high from the ground level. A person standing on the ground wants to feed the monkey. He uses a bow and arrow to launch the food to the monkey. If the person knows that the monkey is going to drop from the tree at the same instant that the person launches the food, how should the person aim the arrow containing the food?
A) He should aim it at the monkey.
For general projectile motion, the horizontal component of a projectile's acceleration
A) is zero.
If the acceleration vector of an object is directed perpendicular to the velocity vector,
A) the object is turning.
For which value of θ is the range of a projectile fired from ground level a maximum?
B) 45° above the horizontal
When a football in a field goal attempt reaches its maximum height, how does its speed compare to its initial speed?
B) It is less than its initial speed.
A pilot drops a bomb from a plane flying horizontally at a constant speed. Neglecting air resistance, when the bomb hits the ground the horizontal location of the plane will
B) be over the bomb.
A rock is thrown upwards at an angle of 40° with respect to the horizontal. As the rock is rising in its trajectory, the vertical component of its velocity
B) decreases.
A student kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory:
B) neither the ball's velocity nor its acceleration is zero.
For a projectile launched horizontally, the horizontal component of a projectile's velocity
B) remains a non-zero constant.
For general projectile motion, the horizontal component of a projectile's velocity
B) remains a non-zero constant.
For general projectile motion, the vertical component of a projectile's acceleration
B) remains a non-zero constant.
Marcia uses a bow to shoot an arrow with initial velocity of magnitude v0 and at an angle θ above the horizontal. When the arrow returns to the same height from which it started,
C) the speed of the arrow is again v0.
A mountain climber encounters a crevasse in an ice field. The opposite side of the crevasse is a height h lower, and is separated horizontally by a distance w. To cross the crevasse, the climber gets a running start and jumps in the horizontal direction. If the height of the crevasse increases but the width remains the same, then,
B) the minimum speed needed to cross the crevasse decreases.
If the acceleration vector of an object is directed parallel to the velocity vector,
B) the object is speeding up.
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. When they reach the lake below,
B) the splashdown speed of John is larger than that of James.
A boy kicks a football with an initial velocity of 20 m/s at an angle of 25° above the horizontal. The magnitude of the acceleration of the ball while it is in flight is
C) 9.8 m/s2
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°. When the snowballs reach the ground below,
C) Both snowballs will hit the ground with the same speed.
A monkey is sitting at the top of a tree 20 m high from the ground level. A person standing on the ground wants to feed the monkey. He uses a bow and arrow to launch the food to the monkey. If the monkey remains seated at the top of the tree, how should the person aim the arrow containing the food so that the monkey gets the food?
C) He should aim it above the monkey.
A rock is thrown at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the velocity of the rock at the highest point of its trajectory?
C) It is equal to its initial horizontal velocity.
A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the velocity of the rock right before it hits the ground?
C) It is equal to the magnitude of its initial velocity.
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.
C) James and John will reach the surface of the lake at the same time.
An athlete throws a ball with a velocity of 40 m/s at an angle of 20° above the horizontal. Which of the following statements is true in this case?
C) The vertical component of the velocity changes sign after the ball attains its maximum height.
For a projectile launched horizontally, the vertical component of a projectile's velocity
C) continuously increases.
A rock is thrown upwards at an angle of 40° with respect to the horizontal. As the rock is rising in its trajectory, the horizontal component of its velocity
C) remains the same.
A ball rolls off the edge of a table. The horizontal component of the ball's velocity remains constant during its entire trajectory because
C) the ball is not acted upon by a force in the horizontal direction.
If the acceleration vector of an object is directed anti-parallel to the velocity vector,
C) the object is slowing down.
A projectile is launched with an initial velocity of 80 m/s at an angle of 30° above the horizontal. Neglecting air resistance, what is horizontal component of the projectile's acceleration?
D) 0 m/s2
A bullet is fired from ground level with a speed of 150 m/s at an angle 30.0° above the horizontal at a location where g = 10.0 m/s2. What is the horizontal component of its velocity when it is at the highest point of its trajectory?
D) 130 m/s
A ball is thrown with a velocity of 40 m/s at an angle of 30° above the horizontal and attains a certain range R. At what other angle will this ball attain the same range keeping its initial velocity the same?
D) 60°
If the initial speed of a projectile is doubled.
D) Its range will quadruple.
A projectile is launched with initial velocity v0 at an angle of 30° above the horizontal. If a second projectile is launched with the same initial velocity but at angle of 60° above the horizontal.
D) The ranges of the two projectiles will be identical.
For which value of θ is the height of a projectile fired from ground level a maximum?
E) 90° above the horizontal
Two objects are thrown vertically upwards simultaneously, one on the surface of Earth and the other on the surface of the Moon. Both have an initial velocity of 20 m/s. Both objects will take the same time to reach the highest point of their trajectory.
FALSE
Two similar objects are thrown simultaneously from the top of a building with the same speed. One is thrown vertically downward, and the other at an angle. Both objects reach the ground at the same time.
FALSE
A ball is thrown at an angle of θ above the horizontal. If there is no acceleration due to gravity the ball will follow a straight-line path.
TRUE
A projectile is launched from ground level with a certain speed. For any range less than the maximum range there are two possible launch angles that give the same range.
TRUE
The horizontal component of the velocity of a projectile remains constant during the entire trajectory of the projectile.
TRUE
The vertical component of the acceleration of a projectile remains constant during the entire trajectory of the projectile.
TRUE