Quiz 7

Balls 1 and 2 are each thrown horizontally from the same height above level ground, but ball 2 has a greater initial velocity after leaving the thrower’s hand. Compare accelerations of the balls and the times it takes them to hit the ground. Air resistance is negligible.

• Acceleration a: Greater for ball 2, Time to hit ground: Greater for ball 2

• Acceleration a: Greater for ball 2, Time to hit ground: Equal

• Acceleration a: Equal, Time to hit ground: Greater for ball 2

• Acceleration a: Equal, Time to hit ground: Equal

The graph above represents position x versus time t for an object moving in a straight line toward the right. Which of the following correctly describes the motion of this object?

• The object’s speed is increasing because of unbalanced forces

• The object’s speed is increasing because of balanced forces

• The object’s speed is decreasing because of unbalanced forces

• The object’s speed is decreasing because of balanced forces

A group of students sets up an Atwood Machine where m₁ = 4 kg and m₂ = 6 kg but the machine accelerates faster than they want for the experiment. Which of the following masses would have exactly half the acceleration of this first Atwood Machine?

• m₁ = 2 kg, m₂ = 6 kg

• m₁ = 3 kg, m₂ = 4 kg

• m₁ = 2 kg, m₂ = 3 kg

• m₁ = 9 kg, m₂ = 11 kg

Which of the following conclusions can the student draw from the graphs, and why? Use the information and graphs provided for reference.

• The horizontally rolled ball travels a greater horizontal distance and takes a longer amount of time to reach the ground.

• The released ball travels with a slower speed and takes a longer amount of time to reach the ground.

• Since both balls have zero horizontal acceleration, they reach the ground at the same time.

• Since the balls have the same vertical position at any given time, they reach the ground at the same time.

Use the graph below for question 5. An object is sliding to the right along a straight line on a horizontal surface. The graph shows the object’s velocity as a function of time. Which of the following statements correctly describes the motion of the object?

• The object has zero acceleration

• The object turns around (changes direction) at t = 4 sec

• The object’s speed is decreasing from t=4 sec to t=8 sec

• The object has a displacement of 64 m during the time shown

Use the graph below for question 6. An engineer measures the velocity v of a remote-controlled cart on a straight track at regular time intervals. When is the car moving at constant, non-zero velocity?

• 3 s ≤ t < 5 s

• 5 s ≤ t < 7 s

• 7 s ≤ t < 10 s

• 10 s ≤ t < 12 s

Two objects, X and Y, accelerate from rest with the same constant acceleration. Object X accelerates for twice as long as Object Y. Which of the following is true of these objects at the end of their respective periods of acceleration?

• Object X is moving at the same speed as object Y.

• Object X is moving four times faster than object Y.

• Object X has traveled twice as far as object Y.

• Object X has traveled four times as far as object Y.

An object begins at position x = 0 and moves one-dimensionally along the x-axis with a velocity v expressed as a function of time t according to the graph above. When does the object come back to its starting point (x = 0)?

• between t = 0 and t = 10 sec

• between t = 10 and t = 20 sec

• between t = 20 and t = 30 sec

• between t = 30 and t = 40 sec

If an object is thrown vertically upward, the direction and magnitude of its acceleration while it is in the air is

• upward and increasing

• upward and constant

• downward and increasing

• downward and constant

A rock is thrown with a horizontal velocity of 6 m/s from a cliff that is 20 m above level ground. The rock travels a horizontal distance $d$ in time $t$ before hitting the ground. Air resistance is negligible. On a second throw the rock has an initial horizontal velocity of 12 m/s. How does the flight of the second throw compare to the first throw?

• Time = t and distance = d

• Time = 2t and distance = 2d

• Time = t and distance = 2d

• Time = 2t and distance = d