AP Physics B : Understanding Vector and Scalar Quantities

Study concepts, example questions & explanations for AP Physics B

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Example Questions

Example Question #1 : Linear Motion

A ball is thrown at a velocity of  at an angle of  from the horizontal. What are the ball's horizontal and vertical velocities?

Ball_32_degrees

Possible Answers:

There is not enough information to solve this problem

Correct answer:

Explanation:

The velocity of  can be broken into horizontal and vertical components by using trigonometry. Think of the figure below, where x and y velocity components of the total velocity are shown.

 Ball_32_degrees_xy

Use the total velocity, the x-component, and the y-component to form a right triangle below.

 Xy_velocities

Treating  as the hypotenuse, x-component as the leg adjacent, and y-component as the leg opposite, you can conclude that the velocities are related through trigonometric identities.

Plugging in the given values, we can solve for the x and y velocity components.

Example Question #1 : Understanding Vector And Scalar Quantities

Which answer choice below includes only scalar quantities?

Possible Answers:

Distance, speed, time

Force, time, velocity

Acceleration, energy, displacement

Velocity, displacement, force

Displacement, time, acceleration

Correct answer:

Distance, speed, time

Explanation:

Scalar quantities are those that can be described with magnitude only, as opposed to vectors, which include both magnitude and direction components. Distance, speed, and time are all scalars. Displacement is not a scalar, as it involves both the distance and the direction moved from a starting point. Velocity also includes a direction component, and is therefore a vector quantity.

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