Physics for Scientists and Engineers, 6e Chapter 2 – Motion in One Dimension

Under which of the following conditions is the magnitude of the average velocity of a particle moving in one dimension smaller than the average speed over some time interval? A particle moves in the + x direction without reversing. 2.A particle moves in the - x direction without reversing. 3.A particle moves in the + x direction and then reverses the direction of its motion. 4.There are no conditions for which this is true.

If the particle moves along a line without changing direction, the displacement and distance traveled over any time interval will be the same. As a result, the magnitude of the average velocity and the average speed will be the same. If the particle reverses direction, however, the displacement will be less than the distance traveled. In turn, the magnitude of the average velocity will be smaller than the average speed.

If a car is traveling eastward and slowing down, what is the direction of the force on the car that causes it to slow down? eastward 2.westward 3.neither of these

If the car is slowing down, a force must be pulling in the direction opposite to its velocity.

Which of the following is true? If a car is traveling eastward, its acceleration is eastward. 2.If a car is slowing down, its acceleration must be negative. 3.A particle with constant acceleration can never stop and stay stopped.

If a particle with constant acceleration stops and its acceleration remains constant, it must begin to move again in the opposite direction. If it did not, the acceleration would change from its original constant value to zero. Choice (1) is not correct because the direction of acceleration is not specified by the direction of the velocity. Choice (2) is also not correct by counterexample – a car moving in the –x direction and slowing down has a positive acceleration.

A ball is thrown upward. While the ball is in free fall, its acceleration increases 2.decreases 3.increases and then decreases 4.decreases and then increases 5.remains constant

For the entire time interval that the ball is in free fall, the acceleration is that due to gravity.

After a ball is thrown upward and is in the air, its speed increases 2.decreases 3.increases and then decreases 4.decreases and then increases 5.remains the same

While the ball is rising, it is slowing down. After reaching the highest point, the ball begins to fall and its speed increases.

Which values represent the ball’s vertical velocity and acceleration at points A, C, and E in the figure below? v y = 0, a y = m/s 2 2.v y = 0, a y = 9.80 m/s 2 3.v y = 0, a y = 0 4.v y = m/s 2, a y = 0

At the highest point, the ball is momentarily at rest, but still accelerating at –g.