Thursday, November 8, 2012

Practice Quiz on Projectile Motion


1) A boy throws a ball at an initial velocity of 26 m/s at an angle of 20e above the horizontal. How high
above the projection point is the ball after 1.4 s?
A) 8.2 m
B) 24 m
C) 23 m
D) 2.8 m
Answer: D


2) The horizontal and vertical components of the initial velocity of a football are 16 m/s and 20 m/s
respectively. How long does it take for the football to rise to the highest point of its trajectory?
A) 1.0 s
B) 2.0 s
C) 3.0 s
D) 4.0 s
Answer: B

3) A ball rolls over the edge of a table with a horizontal velocity v m/s. The height of the table is 1.6 m and
the horizontal range of the ball from the base of the table is 20 m. What is the magnitude and direction of
the ball's acceleration right after it leaves the table?
A) 4.9 m/s2 downward
B) 0 m/s2 downward
C) 19.6 m/s2 downward
D) 9.8 m/s2 downward
Answer: D

4) A hockey puck slides off the edge of a table with an initial velocity of 20 m/s. The height of the table
above the ground is 2.0 m. What is the acceleration of the puck just before it touches the ground?
A) 20 m/s2
B) 4.9 m/s2
C) 19.6 m/s2
D) 9.8 m/s2
Answer: D


5) A ball rolls off the edge of a table. The horizontal component of the ball's velocity remains constant
during its entire trajectory because
A) the ball is not acted upon by any force.
B) the net force acting on the ball is zero.
C) the ball is not acted upon by a force in the horizontal direction.
D) None of the other choices is correct.
Answer: C


6) 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.
B) He should aim it below the monkey.
C) He should aim it above the monkey.
D) None of the other choices is correct.
Answer: A



7) An athlete throws a ball with a velocity of 40 m/s at an angle of 20e above the horizontal. Which of the
following statements is true in this case?
A) The vertical component of the velocity remains constant.
B) The horizontal component of the velocity changes.
C) The vertical component of the velocity changes sign after the ball attains its maximum height.
D) The horizontal component of the velocity changes sign after the ball attains its maximum height.
Answer: C


8) A bullet is fired from ground level with a speed of 150 m/s at an angle 30.0e 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
B) 75.0 m/s
C) 130 m/s
D) 150 m/s
Answer: A


9) For general projectile motion, which statement is true when the projectile is at the initial and final points
of the parabolic path?
A) The magnitude of the x and y components of its velocity are same at both points.
B) The magnitude of its x component of velocity at the initial point is smaller than its magnitude of the y
component of velocity at the final point.
C) The magnitude of its x component of velocity at the initial point is bigger than its magnitude of the y
component of velocity at the final point.
D) The velocity components are zero at both points.
Answer: A


10) 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,
A) the splashdown speed of James is larger than that of John.
B) the splashdown speed of John is larger than that of James.
C) they will both have the same splashdown speed.
D) the splashdown speed of James will always be 9.8 m/s larger than that of John.
Answer: B

11) 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 30e below the horizontal; Debra throws
her snowball upward, at 30e. When the snowballs reach the ground below,
A) Debra's snowball will stay in the air longer than Mary's.
B) Mary's snowball will stay in the air longer than Debra's.
C) Both snowballs will take the same amount of time to hit the ground.
D) Debra's snowball never hits the ground since it is thrown upwards.
Answer: A


12) If the initial speed of a projectile is doubled.
A) Its range will double.
B) Its range will be decreased by a factor of two.
C) Its range will quadruple.
D) Its range will decrease by a factor of four.
Answer: C

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