Projectile Motion Conceptual Questions

Answer each question to the best of your ability. Be sure that you read each question carefully! Is the questioning asking about the objects velocity or acceleration? What about the horizontal or vertical component of those quantities? Or the time to hit the ground? Is the object being launched horizontally? At an angle with a level surface? What about being launched at an angle from the top of a cliff to the ground below?

______1. A boulder rolls horizontally off of a very high cliff and experiences no significant air resistance. While it is falling, its trajectory is never truly vertical.

  1. True
  2. False

______2.For general projectile motion with no air resistance, the horizontal component of a projectile's velocity

  1. Remains zero
  2. Remains a non-zero constant
  3. Continuously increases
  4. Continuously decreases
  5. First decreases then increases

______3.For general projectile motion with no air resistance, the horizontal component of a projectile's acceleration

  1. Remains zero
  2. Remains a non-zero constant
  3. Continuously increases
  4. Continuously decreases
  5. First decreases then increases

______4.For general projectile motion with no air resistance, the vertical component of a projectile's acceleration

  1. Remains zero
  2. Remains a non-zero constant
  3. Continuously increases
  4. Continuously decreases
  5. First decreases then increases

______5.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.

  1. The thrown pebble hits first
  2. The dropped pebble hits first
  3. They hit at the same time
  4. We cannot tell without which pebble is heavier

______6.Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance?

  1. The speed of the object is constant but its velocity is not constant
  2. The acceleration of the object is +g when the object is rising and -g when it is falling
  3. The acceleration of the object is zero at its highest point
  4. The speed of the object is zero at its highest point
  5. The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward

______7.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?

  1. It is impossible to tell because we do not know their masses
  2. the stone
  3. the ball
  4. Both are traveling at the same speed

______8.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

  1. be behind the package
  2. be directly over the package
  3. be in front of the package
  4. depend on the speed of the plane when the package was released

______9.A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory

  1. both the velocity and the acceleration of the soccer ball are zero
  2. neither the ball's velocity nor its acceleration are zero
  3. the ball's acceleration is zero but its velocity is not zero
  4. the ball's acceleration points upward
  5. the ball's velocity points downward

______10.A ball is thrown with an initial velocity of 20 m/s at an angle of 60° above the horizontal. If we can neglect air resistance, what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

  1. 10 m/s
  2. 17 m/s
  3. 20 m/s
  4. Zero

______11.An object is launched at an angle to the horizontal on a long, flat firing range. Which launch angle will produce the longest range? Assume air resistance is negligible.

  1. 30 degreesc. 60 degrees
  2. 45 degreesd. 90 degrees

______12.A ball is thrown at an original speed of 8.0 m/s at an angle of 35° above the horizontal. If there is no air resistance, what is the speed of the ball when it returns to the same horizontal level?

  1. 4.0 m/s
  2. 8.0 m/s
  3. 16 m/s
  4. 9.8 m/s

______13.A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.3 s. What is the height of the cliff if air resistance is negligible?

  1. 22 m
  2. 43 m
  3. 77 m
  4. 91 m

______14.A girl throws a rock horizontally, with a velocity of 10 m/s, from a bridge. It falls 20 m to the water below. How far does the rock travel horizontally before striking the water, assuming negligible air resistance?

  1. 14 m
  2. 16 m
  3. 20 m
  4. 24 m

______15.A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown, assuming negligible air resistance?

  1. 6.1 m/s
  2. 7.4 m/s
  3. 8.1 m/s
  4. 8.9 m/s

______16.A boy throws a rock with an initial velocity of 3.13 m/s at 30.0° above the horizontal. How long does it take for the rock to reach the maximum height of its trajectory if air resistance is negligibly small?

  1. 0.160 s
  2. 0.282 s
  3. 0.313 s
  4. 0.441 s