1. A train is traveling along a straight, horizontal track with a constant accel

Question

1. A train is traveling along a straight, horizontal track with a constant acceleration in the forward direction. At the instant the speed is 50 mph, a ball is dropped by an observer in the train. The observer in the train determines that the horizontal speed of the ball during the fall is
A. decreasing. B. increasing. C. zero. D. equal to 50 mph.
2.A ball is thrown horizontally at 30 m/s from a flatcar that is moving in a straight line at 40 m/s. Relative to a person on the ground, what is the horizontal speed of the ball when it is thrown in the forward direction?
A. 10 m/s B. 30 m/s C. 50 m/s D. 70 m/s
3. An aircraft carrier is moving to the north at a constant 25 mph on a windless day. A plane requires a speed relative to the air of 125 mph to take off. How fast must the plane be traveling relative to the deck of the aircraft carrier to take off if the plane is headed south?
A. 25 mph B. 100 mph C. 125 mph D. 150 mph
4. What would an observer measure for the magnitude of the free-fall acceleration in an elevator near Earth's surface if the elevator accelerates upward at 6 m/s2?
A. 4 m/s2 B. 6 m/s2 C. 10 m/s2 D. 16 m/s2
5. A space station, far from any large masses, can be spun so that people inside the station feel the effects of an "artificial gravity." This works because
A.the station is an inertial reference system. B. the people experience an inertial force.
C. living in outer space doesn't require an "up" or "down" direction. D. gravity extends throughout space.
6. Any reference system moving with a constant velocity with respect to an inertial system is known as an accelerating reference system.
A. True B. False
7. A train is traveling along a straight, horizontal track at a constant speed that is only slightly less than that of light. If an observer in the train drops a ball and an observer on the ground measures its acceleration, she will obtain a value
A. equal to g B. greater than g C. less than g
1. A train is traveling along a straight, horizontal track with a constant acceleration in the forward direction. At the instant the speed is 50 mph, a ball is dropped by an observer in the train. The observer in the train determines that the horizontal speed of the ball during the fall is
A. decreasing. B. increasing. C. zero. D. equal to 50 mph.
2.A ball is thrown horizontally at 30 m/s from a flatcar that is moving in a straight line at 40 m/s. Relative to a person on the ground, what is the horizontal speed of the ball when it is thrown in the forward direction?
A. 10 m/s B. 30 m/s C. 50 m/s D. 70 m/s
3. An aircraft carrier is moving to the north at a constant 25 mph on a windless day. A plane requires a speed relative to the air of 125 mph to take off. How fast must the plane be traveling relative to the deck of the aircraft carrier to take off if the plane is headed south?
A. 25 mph B. 100 mph C. 125 mph D. 150 mph
4. What would an observer measure for the magnitude of the free-fall acceleration in an elevator near Earth's surface if the elevator accelerates upward at 6 m/s2?
A. 4 m/s2 B. 6 m/s2 C. 10 m/s2 D. 16 m/s2
5. A space station, far from any large masses, can be spun so that people inside the station feel the effects of an "artificial gravity." This works because
A.the station is an inertial reference system. B. the people experience an inertial force.
C. living in outer space doesn't require an "up" or "down" direction. D. gravity extends throughout space.
6. Any reference system moving with a constant velocity with respect to an inertial system is known as an accelerating reference system.
A. True B. False
7. A train is traveling along a straight, horizontal track at a constant speed that is only slightly less than that of light. If an observer in the train drops a ball and an observer on the ground measures its acceleration, she will obtain a value
A. equal to g B. greater than g C. less than g
1. A train is traveling along a straight, horizontal track with a constant acceleration in the forward direction. At the instant the speed is 50 mph, a ball is dropped by an observer in the train. The observer in the train determines that the horizontal speed of the ball during the fall is
A. decreasing. B. increasing. C. zero. D. equal to 50 mph.
2.A ball is thrown horizontally at 30 m/s from a flatcar that is moving in a straight line at 40 m/s. Relative to a person on the ground, what is the horizontal speed of the ball when it is thrown in the forward direction?
A. 10 m/s B. 30 m/s C. 50 m/s D. 70 m/s
3. An aircraft carrier is moving to the north at a constant 25 mph on a windless day. A plane requires a speed relative to the air of 125 mph to take off. How fast must the plane be traveling relative to the deck of the aircraft carrier to take off if the plane is headed south?
A. 25 mph B. 100 mph C. 125 mph D. 150 mph
4. What would an observer measure for the magnitude of the free-fall acceleration in an elevator near Earth's surface if the elevator accelerates upward at 6 m/s2?
A. 4 m/s2 B. 6 m/s2 C. 10 m/s2 D. 16 m/s2
5. A space station, far from any large masses, can be spun so that people inside the station feel the effects of an "artificial gravity." This works because
A.the station is an inertial reference system. B. the people experience an inertial force.
C. living in outer space doesn't require an "up" or "down" direction. D. gravity extends throughout space.
6. Any reference system moving with a constant velocity with respect to an inertial system is known as an accelerating reference system.
A. True B. False
7. A train is traveling along a straight, horizontal track at a constant speed that is only slightly less than that of light. If an observer in the train drops a ball and an observer on the ground measures its acceleration, she will obtain a value
A. equal to g B. greater than g C. less than g

Explanation / Answer

1.
Once the ball is dropped, it doesn't have any horizontal acceleration with respect to an outside observer.
Since the observer in the train is moving with an acceleration relative to the ball, according to her, the ball's speed is decreasing.

2.
Speed with respect to ground = Speed of the flat car with respect to the ground + Speed of the ball with respect to the flatcar
= 40 + 30
= 70 mph

3.
Speed of plane with respect of air = Speed of aircraft carrier with respect to air + speed of plane with respect to aircraft carrier
125 = - 25 + Speed of plane with respect to aircraft carrier            
peed of plane with respect to aircraft carrier = 125 + 25
= 150 mph

4.
Net acceleration = 6 - (-10)
= 16 m/s2.

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