Direction of Velocity at Various Times in Flight for Projectile Motion Conceptua

Question

Direction of Velocity at Various Times in Flight for Projectile Motion Conceptual Question

For each of the motions described below, determine the algebraic sign (positive, negative, or zero) of the x component and y component of velocity of the object at the time specified. For all of the motions, the positive x axis points to the right and the positive y axis points upward.

Alex, a mountaineer, must leap across a wide crevasse.(Figure 1) The other side of the crevasse is below the point from which he leaps, as shown in the figure. Alex leaps horizontally and successfully makes the jump.

Part A

Determine the algebraic sign of Alex's x velocity and y velocity at the instant he leaves the ground at the beginning of the jump.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

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Part B

Determine the algebraic signs of Alex's x velocity and y velocity the instant before he lands at the end of the jump.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

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At the buzzer, a basketball player shoots a desperation shot. The ball goes in!(Figure 2)

Part C

Determine the algebraic signs of the ball's x velocity and y velocity the instant after it leaves the player's hands.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

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Part D

Determine the algebraic signs of the ball's x velocity and y velocity at the ball's maximum height.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

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Figure 1Figure 2 of 2

Direction of Velocity at Various Times in Flight for Projectile Motion Conceptual Question

For each of the motions described below, determine the algebraic sign (positive, negative, or zero) of the x component and y component of velocity of the object at the time specified. For all of the motions, the positive x axis points to the right and the positive y axis points upward.

Alex, a mountaineer, must leap across a wide crevasse.(Figure 1) The other side of the crevasse is below the point from which he leaps, as shown in the figure. Alex leaps horizontally and successfully makes the jump.

Part A

Determine the algebraic sign of Alex's x velocity and y velocity at the instant he leaves the ground at the beginning of the jump.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

SubmitHintsMy AnswersGive UpReview Part

Part B

Determine the algebraic signs of Alex's x velocity and y velocity the instant before he lands at the end of the jump.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

SubmitHintsMy AnswersGive UpReview Part

At the buzzer, a basketball player shoots a desperation shot. The ball goes in!(Figure 2)

Part C

Determine the algebraic signs of the ball's x velocity and y velocity the instant after it leaves the player's hands.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

SubmitHintsMy AnswersGive UpReview Part

Part D

Determine the algebraic signs of the ball's x velocity and y velocity at the ball's maximum height.

Type the algebraic signs of the x velocity and the y velocity separated by a comma (examples: +,- and 0,+).

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Figure 1Figure 2 of 2

Explanation / Answer

part-a positive, 0
Algebraic sign of velocity The algebraic sign of the velocity is determined solely by comparing the direction in which the object is moving with the direction that is defined to be positive. In this example, to the right is defined to be the positive x direction and upward the positive y direction. Therefore, any object moving to the right, whether speeding up, slowing down, or even simultaneously moving upward or downward, has a positive x velocity. Similarly, if the object is moving downward, regardless of any other aspect of its motion, its y velocity is negative
part-b positive, negative
Sketch Alex’s final velocity On the diagram below, sketch the vector representing Alex’s velocity the instant before he safely lands on the other side of the crevasse.
part-c
positive, positive
Sketch the basketball’s initial velocity On the diagram below, sketch the vector representing the velocity of the basketball the instant after it leaves the player’s hands.
part-D

positive, zero
Sketch the basketball’s velocity at maximum height Typesetting math: 100% On the diagram below, sketch the vector representing the velocity of the basketball the instant it reaches its maximum height

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