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Question 17 of 36

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SAT Subject Test

The figure shows an upward-swinging pendulum consisting of a ball on a string. It is halfway to its highest position. Various paths of the pendulum’s ball are shown via arrows, as follows: A: Vertically downward B. A downward-curving path close to A C. A downward-curving path farther away from A D. A downward-curving path close to E E. A straight path perpendicular to the string

A pendulum is swinging upward and is halfway toward its highest position, as shown above, when the string breaks. Which of the paths shown best represents the one that the ball would take after the string breaks?

Select an Answer

A

Correct Answer: 
No

B

Correct Answer: 
No

C

Correct Answer: 
No

D

Correct Answer: 
Yes

E

Correct Answer: 
No

As the pendulum swings in an arc, the velocity at any instant is tangent to the arc and therefore perpendicular to the string. The ball has this velocity at the instant the string breaks, so the initial part of the path must be perpendicular to the string. Afterwards, the ball behaves as a projectile under the influence of gravity alone, so it follows a parabolic path.

Question Difficulty: 
medium