4) An airplane that flies at 100 km/h in a 100 km/h hurricane crosswind has a ground speed of A) 0 km/h. B) 100 km/h. C) 141 km/h. D) 200 km/h.

Transcription

1 10.1 Questions About Projectile Motion 3) Which of the following is not a vector quantity? A) velocity B) speed C) acceleration D) None are vector quantities. E) All are vector quantities. 4) An airplane that flies at 100 km/h in a 100 km/h hurricane crosswind has a ground speed of A) 0 km/h. B) 100 km/h. C) 141 km/h. D) 200 km/h. 5) An airplane travels at 141 km/h toward the northeast. What is its component of velocity due north? A) 41 km/h B) 100 km/h C) 110 km/h D) 141 km/h Figure 10-B 6) A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its vertical component of velocity A) increases. B) remains unchanged. C) decreases. 7) A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity A) increases. B) remains unchanged. C) decreases. 8) A stone is thrown horizontally from the top of a cliff. One second after it has left your hand, its vertical distance below the top of the cliff is A) 5 m. B) 10 m. C) 15 m.

2 9) Throw an object upward at a 45 degree angle. With no gravity it will follow a straight-line path. But because of gravity, at the end of 1 second, it is A) about 5 m below the straight line. B) about 10 m below the straight line. C) about 15 m below the straight line. 10) Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity A) decreases. B) remains constant. C) increases. 11) A bullet fired horizontally from a rifle begins to fall A) as soon as it leaves the barrel. B) after air friction reduces its speed. C) neither of these 12) A projectile is launched vertically upward at 50 m/s. If air resistance is negligible, its speed upon returning to its starting point is A) less than 50 m/s. B) 50 m/s. C) more than 50 m/s. 15) A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of velocity because A) it is not acted on by any forces. B) it is not acted on by any horizontal forces. C) it has no vertical component of velocity to begin with. D) the net force acting on it is zero. 16) A hunter on level ground fires a bullet at an angle of 10 degrees above the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first? A) the dropped one B) the fired one 17) A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first? A) the dropped one B) the fired one

3 18) A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in A) less than 0.5 s. B) more than 0.5 s. C) 0.5 s. 19) An object is dropped and freely falls to the ground with an acceleration of 1 g. If it is thrown upward at an angle instead, its acceleration will be A) 0 g. B) 1 g downward. C) 1 g upward. D) larger than 1 g. 20) A projectile is launched at ground level an angle of 15 degrees above the horizontal and lands down range. What other projection angle for the same speed would produce the same down-range distance? A) 30 degrees B) 45 degrees C) 50 degrees D) 75 degrees E) 90 degrees 21) A projectile is fired into the air at an angle of 50 degrees with the ground and lands on a target that is at the same level at which the projectile started. It will also land on the target if it is fired at an angle of A) 40 degrees. B) 45 degrees. C) 55 degrees. D) 60 degrees. 22) A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 second later? A) 50 m B) 98 C) 100 D) 490

4 23) Two projectiles are fired from ground level at equal speeds but different angles. One is fired at an angle of 30 degrees and the other at 60 degrees. The projectile to hit the ground first will be the one fired at (neglect air resistance) A) 30 degrees. B) 60 degrees. 24) After a rock thrown straight up reaches the top of its path and then falls a short distance, its acceleration is (neglect air resistance) A) greater than when it was at the top of its path. B) less than when it was at the top of its path. C) the same as it was at the top of its path. 26) The ground speed of an airplane that has an airspeed of 200 km/h when it is in a 200-km/h crosswind is A) 0 km/h. B) 200 km/h. C) 283 km/h. D) 400 km/h. E) 1600 km/h. 29) An object is thrown vertically into the air. Because of air resistance, the time for its descent will be A) longer than the ascent time. B) shorter than the ascent time. C) equal to the ascent time. D) Not enough information given to say. 30) A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The player sees the ball land 20 m down range. What is the player's pitching speed? A) about 5 m/s B) about 10 m/s C) about 20 m/s D) about 25 m/s 31) An airplane flies at 40 m/s at an altitude of 50 meters. The pilot drops a heavy package which falls to the ground. Where, approximately, does the package land relative to the plane's new position? A) beneath the plane B) 400 m behind the plane C) 500 m behind the plane D) more than 500 m behind the plane

5 32) A bullet is fired horizontally with an initial velocity of 300 m/s from a tower 20 m high. If air resistance is negligible, the horizontal distance the bullet travels before hitting the ground is about A) 200 m. B) 300 m. C) 400 m. D) 500 m. E) 600 m. 33) A river 100 m wide flows due south at 1 m/s. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat reaches the east bank A) due east of where it started. B) 141 m farther south than where it started. C) 100 m farther south than where it started. D) 100 m farther north than where it started. 34) A river 100 m wide flows due south. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. Relative to the Earth, the boat travels A) nowhere. B) 141 m. C) 100 m. D) 200 m. E) 241 m. 35) A river 100 m wide flows due south. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat crosses in A) 50 s. B) 100 s. C) 141 s. D) 200 s. 36) A river 100 m wide flows due south at 1 m/s. A boat that goes 1 m/s relative to the water leaves the west bank. To land at a point due east of its starting point, the boat must be pointed A) northeast. B) east. C) southeast. D) nowhere it can't be done.