Unit: Motion in a Plane
Year: 1996 Question#: 58
Question: If the angle of elevation of the cannon is decreased from 35 degrees to 30 degrees, the vertical component of the ball's initial velocity will
(1 ) decrease and its horizontal component will decrease
(2 ) decrease and its horizontal component will increase
(3 ) increase and its horizontal component will decrease
(4 ) increase and its horizontal component will increase
What is this question really asking?
Explanation by: Ben H
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Answer 1
decrease and its horizontal component will decrease
INCORRECT
No matter what angle the cannon is pointed at, it will always shoot the cannonball at an initial velocity Vi. If the angle is changed, though, the component velocities may change. With the angle decreased to 30 degrees, the vertical component must decrease, but the horizontal component must increase, or the total Vi of the cannonball would be smaller than if it was fired at the origonal angle. return to top
Answer 2
decrease and its horizontal component will increase
CORRECT With the decrease in the angle, the vertical component must also decrease, but to compensate for this loss of velocity, the horizontal component must increase in order to keep the same Vi. return to top
Answer 3
increase and its horizontal component will decrease
INCORRECT
The vertical velocity component could not increase with a decreased angle.
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Answer 4
increase and its horizontal component will increase
INCORRECT
If this was true, then the decrease in the cannon's angle would result in both an increased total velocity and an increased vertical velocity, which cannot happen with just a decrease in the angle.
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What's this question really asking?
What happens to the component velocities of a vector as the vector's angle is changed? return to top
