- Joined
- Jan 30, 2009
- Messages
- 4,218
- Reaction score
- 14
From the passage, there are two cannons. One is on a cliff, the other is on the ground. They're both pointing directly at each other. Cannon A is the one on the cliff, Cannon B is the one on the ground.
The question is
Using the setup shown in Figure 1, can a cannonball fired from Cannon A ever hit Cannon B?
A. Yes, if the speed of the ball upon exiting Cannon A is sufficiently large.
B. Yes, if the exit speed equals the speed the ball gains by falling 32 m.
C. Yes, regardless of the exit speed.
D. No.
The answer is D, with the explanation
Since the two cannons are aimed at each other, the cannonball would travel along a straight path and hit Cannon B if there were no gravity. But there is gravity. Gravity will change the path of the ball, specifically causing the ball to drop below this straight path. No matter how fast the cannonball travels, gravity will always cause it to drop below this line and therefore miss Cannon B.
I put choice A, and I still feel like it's the right answer. As the velocity of the ball approaches infinity, the time of travel approaches zero and thus the change in velocity and thus change in height due to gravity both approach zero as well. It doesn't state in the passage that the cannons are dimensionless (it even gives the barrels a length of 2.5 m).
What do you all think?
The question is
Using the setup shown in Figure 1, can a cannonball fired from Cannon A ever hit Cannon B?
A. Yes, if the speed of the ball upon exiting Cannon A is sufficiently large.
B. Yes, if the exit speed equals the speed the ball gains by falling 32 m.
C. Yes, regardless of the exit speed.
D. No.
The answer is D, with the explanation
Since the two cannons are aimed at each other, the cannonball would travel along a straight path and hit Cannon B if there were no gravity. But there is gravity. Gravity will change the path of the ball, specifically causing the ball to drop below this straight path. No matter how fast the cannonball travels, gravity will always cause it to drop below this line and therefore miss Cannon B.
I put choice A, and I still feel like it's the right answer. As the velocity of the ball approaches infinity, the time of travel approaches zero and thus the change in velocity and thus change in height due to gravity both approach zero as well. It doesn't state in the passage that the cannons are dimensionless (it even gives the barrels a length of 2.5 m).
What do you all think?