Projectiles (Doug G7 Ch3 - Conceptual)

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

• False

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

• remains zero.

• remains a non-zero constant.

• continuously increases.

• continuously decreases.

• first decreases and then increases.

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

• is always zero.

• remains a non-zero constant.

• continuously increases.

• continuously decreases.

• first decreases and then increases.

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

• is always zero.

• remains a non-zero constant.

• continuously increases.

• continuously decreases.

• first decreases and then increases.

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.)

• The speed of the object is constant but its velocity is not constant.

• The acceleration of the object is +9 when the object is rising and -9 when it is falling.

• The acceleration of the object is zero at its highest point.

• The speed of the object is zero at its highest point.

• The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.

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?

• It is impossible to tell because we do not know their masses.

• The stone

• The ball

• Both are traveling at the same speed.

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.

• The thrown pebble hits first.

• The dropped pebble hits first.

• They hit at the same time.

• We cannot tell without knowing which pebble is heavier.

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

• be behind the package.

• be directly over the package.

• be in front of the package.

• depend on the speed of the plane when the package was released.

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

• the splashdown speed of James is larger than that of John.

• the splashdown speed of John is larger than that of James.

• they will both have the same splashdown speed.

• the splashdown speed of James must be 9.8 m/s larger than that of John.

• the splashdown speed of John must be 25 m/s larger than that of James.

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) James reaches the surface of the lake first.

• B) John reaches the surface of the lake first.

• C) James and John will reach the surface of the lake at the same time.

• D) Cannot be determined without knowing the mass of both James and John.