Show:
Displacement & Velocity
Constant Acceleration
Freefall
Graphing
Potpourri
100
If an object is located 20 m to the right of the origin at 1:00 PM and later the object is located 30 m to the right of the origin at 2:00 PM, what is the displacement from 1:00 PM to 2:00 PM?
10 m to the right
100
A ball initially at rest rolls down a hill and has an acceleration of 3.3 m/s^2. If it accelerates for 7.5 s, how far will it move during this time?
93 m
100
True or False: When a ball is thrown straight up, both its velocity and acceleration are zero at the top of its flight.
False Explanation: Velocity is zero but acceleration is still 9.8 m/s2 downward.
100
What does the area between a velocity vs. time graph and the horizontal axis represent?
Displacement
100
A car travels at 50.0 km/hr for 2.00 hours. It then travels an additional distance of 40.0 km in 1.00 hour. The average speed of the car for the entire trip is
46.7 km/hr
200
True or False: Velocity and displacement always have the same sign (positive or negative).
True! Explanation: The sign of both velocity and displacement tell you the direction of motion.
200
True or False: Acceleration always has the same sign as displacement.
False! Explanation: If an object is slowing down, the acceleration will have the opposite sign from displacement.
200
A freely falling object is found to be moving downward at 18 m/s. If it continues to fall, two seconds later the object would be moving with a speed of _____.
38 m/s
200
True or False: An acceleration vs. time graph with a horizontal line below the time axis represents an object slowing down uniformly.
False Explanation: The object could be speeding up if the velocity is also in the negative direction.
200
A car traveling at 4.0 m/s has a constant acceleration of 2.0 m/s^2. After 3.0 seconds, the average velocity during the acceleration is
7.0 m/s
300
True or False: If the average speed is zero, then the average velocity must be zero.
True! Explanation: If average speed is zero, distance must be zero, therefore displacement & velocity are also zero.
300
A car starting from rest travels a distance of 20.0 m with a constant acceleration of 2.0 m/s^2. The car then slows to a stop in 10.0 seconds with a constant acceleration. What is the distance traveled by the car, assuming it moves in a straight line?
65 m
300
True or False: A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun straight down towards the water. If air resistance is negligible, the acceleration of the bullets just before they strike the water is greater for the fired bullet.
False! Explanation: All objects fall at the same rate (g) in the absence of air resistance.
300
True or False: If a position vs. time graph has a negative, constant slope, the acceleration must be negative.
False Explanation: If the slope of a position vs. time graph is constant, the acceleration is zero.
300
Starting from rest, a car that is accelerating uniformly takes 15 m to reach a velocity of v. Under the same driving conditions, how far would the car have to travel to reach a velocity of 2 v?
60 m
400
A bus travels from El Paso, Texas, to Chihuahua, Mexico, in 5.2 h with an average velocity of 73 km/h to the south. What is the bus’ displacement?
380 km south
400
Which of the following have a zero acceleration? 1. Airplane flying level due east at a constant 500 mph 2. Child on a spinning merry-go-round 3. Ball thrown straight up at its highest point 4. Ball reversing direction after rolling up a straight track
1 only
400
An arrow is shot straight up in the air at an initial speed of 15.0 m/s. After how much time is the arrow heading downward at a speed of 8.0 m/s?
2.35 s
400
What is the shape of a position vs. time graph for an object traveling in the positive direction and speeding up?
Half of a concave-up parabola
400
A rock is thrown downward from the top of a 40.0 m tower with an initial speed of 12 m/s. Assuming negligible air resistance, what is the speed of the rock just before hitting the ground?
30 m/s
500
True or False: The average speed can never be greater than the magnitude of the average velocity.
False! Explanation: Average speed = distance/time and Average velocity = displacement/time Distance can be greater than displacement (for example: if you travel in a circle, distance is the circumference of the circle, displacement is zero!
500
A certain airport runway of length L allows planes to accelerate uniformly from rest to takeoff speed using the full length of the runway. Because of the newly designed, the takeoff speed must be doubled, again using the full length of the runway and having the same acceleration as before. In terms of L, what must be the new length of the runway?
4L
500
True or False: When a rocket in freefall is traveling upward, both its acceleration and velocity are directed upward.
False Explanation: Velocity is upward but acceleration is downward.
500
Describe a velocity vs. time graph for an object thrown up in the air and caught at the same height.
A straight line with a negative slope, beginning above the horizontal axis and ending below the horizontal axis.
500
What does the slope of an acceleration vs. time graph represent?
Jerk