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Question 30 of 36

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SAT Subject Test

The figure presents the top view of a disk and a post on level ice. The disk has a mass of 4 kilograms. To the right of the disk is an arrow pointing to the right and labeled 1 meter per second. The post is represented by a square, and the square is oriented so that the sides are at 45 degrees to the horizontal and vertical. Compass directions are shown as North toward the top of the page, South toward the bottom, East toward the right, and West toward the left. Two dashed lines show the path of the disk. The first dashed line is horizontal, and extends from the arrow at the right of the disk to the upper left diagonal side of the square. The other dashed line starts where the first dashed line ends, extends vertically upward, and ends with an arrow pointing to the top of the page, near the top of the figure.

A 4-kilogram disk slides over level ice toward the east at a velocity of 1 meter per second, as shown above. The disk strikes a post and rebounds toward the north at the same speed. The change in the magnitude of the eastward component of the momentum of the disk is

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negative 4 invisible times text   end text kg invisible times times straight m divided by straight s

Correct Answer: 
Yes

negative 1 invisible times text   end text kg invisible times times straight m divided by straight s

Correct Answer: 
No

0 invisible times text   end text kg invisible times times straight m divided by straight s

Correct Answer: 
No

1 invisible times text   end text kg invisible times times straight m divided by straight s

Correct Answer: 
No

4 invisible times text   end text kg invisible times times straight m divided by straight s

Correct Answer: 
No

The correct answer is Error converting from MathML to accessible text.. The momentum of an object is given by the product of the mass of the object and its velocity. Before the collision, the disk is moving directly east, so the eastward component of its momentum is Error converting from MathML to accessible text.. After the collision, the disk is moving directly north so the eastward component of its momentum is zero. Thus the change in the eastward component of momentum is the final value minus the initial value, or left parenthesis 0 minus 4 right parenthesis straight k straight g straight invisible times straight times straight m straight divided by straight s, which is equal to Error converting from MathML to accessible text..

Question Difficulty: 
hard