Kinematics
A cat falls out of a tree that is 7.5m high. Assuming up is positive, down is negative, and the magnitude of the acceleration of gravity is 9.81 m/s^2, what is the cat's final velocity the moment before it hits the ground?
-12m/s
An object is thrown upwards with a velocity of 30 m/s near the surface of the earth. At the peak of its trajectory, what would be the direction of the displacement, velocity, and acceleration?
0,0,Negative
True or False? Gravity pulls with the same force on all objects, regardless of their mass.
False
True or False? In free fall the velocity in an upward path is equal to velocity in a downward path.
False
True or False? In free fall the time in the upward path is equal to time in the downward path.
True
Two objects can have the same position but different velocities. T/F
True
Two objects can have the same speed but different velocities. T/F
True
As an object falls, assuming no air resistance, its acceleration is...
constant
Marcus Aurelius accelerates at -4 m/s2 on his skateboard from rest for 10 seconds. What is his position at the end of the 10 seconds? What is the velocity of Marcus at the end of the 10 seconds?
-200m, -40m/s
Marcus and Malcolm, riding in a stroller, brake from 35 m/s to a stop over a distance of 100.0 m. What is the acceleration of the kitties?
-6.1m/s2
A stone is thrown straight up. What is its acceleration on the way up? What is its acceleration at the peak of its trajectory? What is its acceleration on the way down?
-9.81m/s2 the whole time
What is an object's acceleration when it has reached terminal velocity?
0
Kiwi accelerates on her bicycle from rest to 38 km/hr in 15.2 seconds. What is her acceleration during this time?
0.69m/s2
A bear jumps into a manhole and hits the bottom 1.41 s later. Determine the depth of the manhole.
9.75m
A measurement of an object's change in velocity during some time interval. (a = Δv/Δt). Standard units are m/s2.
Acceleration
A measurement of an object's velocity over the course of some time interval. (can be measured)
Average velocity
The heading of an object, relative to some origin (East, West, North, South, positive, negative, etc.)
Direction
The difference between the final and initial positions of an object. (For example, run 1 lap around a track, displacement = 0m). Standard units are meters.
Displacement
The total sum of the ground/space covered by an object. (For example, run 1 lap around a track, distance = 400m). Standard units are meter.
Distance
A theoretical calculation of an object's velocity at one specific moment in time. (cannot be measured)
Instantaneous Velocity
An object is thrown upwards with a velocity of 30 m/s near the surface of the earth. On the way down, what would be the direction of the displacement, velocity, and acceleration?
Negative, Negative, Negative
A measurement of the location of an object, relative to some origin.
Position
An object is thrown upwards with a velocity of 30 m/s near the surface of the earth. On the way up, what would be the direction of the displacement, velocity, and acceleration?
Positive, Positive, Negative
Suppose you throw a rock nearly straight up at a coconut in a palm tree and the rock just misses the coconut on the way up but hits the coconut on the way down. Neglecting air resistance and the slight horizontal variation in motion to account for the hit and miss of the coconut, how does the speed of the rock when it hits the coconut on the way down compare with what it would have been if it had hit the coconut on the way up? Is it more likely to dislodge the coconut on the way up or down? Explain.
Same speed, opposite velocity, better to hit it down to help gravity.
A number with only a magnitude. Example: 10 kg
Scalar
A measurement of how fast an object is moving. Calculated by dividing distance traveled by the change in time. (s = distance/Δt) Example: 10 m/s. Standard units are m/s.
Speed
Acceleration is a vector, meaning it is a measurement of both magnitude and direction. T/F
True
An object can have a negative position and a positive velocity. T/F
True
A number with a magnitude and a direction. Example: 10 m East.
Vector
A measurement of how fast an object is moving in a certain direction. (v = displacement/Δt). Example: 10 m/s south. Standard units are m/s.
Velocity
A vintage bi-plane has an air speed of 80.0 miles per hour. How long would it take to travel in this plane to Reno Nevada, which is 1600 km away? (Be careful of units and sig figs!) (1 km is 0.621 mi) a. 12 hours b. 20 hours c. 20. hours d. 12.4 hours
a
Marcus Aurelius hears food being served in his cat bowl, and runs from his bed to the cat bowl at 2.7 m/s. It takes him 5.0 seconds to get to his cat bowl. How far away is his bed from his cat bowl? (Be careful of sig figs!) a. 14 m b. 13.5 m c. 15 m d. 1.9 m
a
A ball is thrown straight up, as pictured above. Assuming the point of release is the origin, and up is positive, and down is negative, which of the following statements is true about the ball on the way up? a. the position is positive b. the velocity is positive c. the acceleration is positive
a, b
Which of the following statements are true of projectiles? a. A projectile is a free-falling object. b. A projectile experiences negligible or no air resistance. c. A projectile must be moving in the downward direction. d. A projectile must be accelerating in the downward direction. e. A projectile does not have to have horizontal motion. f. A projectile could begin its projectile motion with a downward velocity. g. A projectile does not need to be "falling."
a, b, d, e, f, g
A ball is thrown straight up, as pictured above. Assuming the point of release is the origin, and up is positive, and down is negative, which of the following statements is true about the ball at the peak of the trajectory? a. the position is positive b. the acceleration is zero c. the velocity is zero
a, c
slope of velocity vs. time
acceleration
area under acceleration vs. time
average velocity
A stone is thrown straight up. When it reaches its highest point, a. Both it's velocity and its acceleration are zero b. It's velocity is zero and its acceleration is not zero c. It's velocity is not zero and its acceleration is zero d. Neither it's velocity nor its acceleration is zero
b
Which of the following statements are true of the time of flight for a projectile? a. The time that a projectile is in the air is dependent upon the horizontal component of the initial velocity. b. The time that a projectile is in the air is dependent upon the vertical component of the initial velocity. c. For a projectile which lands at the same height that it is projected from, the time to rise to the peak is equal to the time to fall from its peak to the original height. d. For the same upward launch angles, projectiles will stay in the air longer if the initial velocity is increased. e. Assume that a kicked ball in football is a projectile. If the ball takes 3 seconds to rise to the peak of its trajectory, then it will take 6 seconds to fall from the peak of its trajectory to the ground.
b, c, d
You run 1 full lap around a 400m track in 100 seconds. Which of the following statements are true? (Check all that apply) a. Your displacement is 400m. b. It's possible at one point during the race you turned around and ran backwards for several seconds. c. Your distance is 400m. d. It's possible at one point during the race you could have been running at 12 m/s. e. Your average velocity is 4 m/s. f. Your average speed is 4 m/s. g. It's possible you may have run north more than you ran south.
b, c, d, f
A mouse and an elephant are dropped from the same height at the same time. Assuming no air resistance, the animal that hits the ground first is...
both animals hit the ground at the same time
A bullet is fired horizontally and hits the ground in 0.5 seconds. If it had been fired with twice the speed in the same direction, it would have hit the ground in ____. (Assume no air resistance.) a. less than 0.5 s. b. more than 0.5 s. c. 0.5 s.
c
An object is thrown straight up with a speed of 10 m/s. Assuming that there is significant air resistance, what will be the speed of the object when it returns to the height from which is was thrown? a. greater than 10 m/s b. 10 m/s c. less than 10 m/s
c
At what point in its path is the vertical component of the velocity (vy) of a projectile the smallest? a. The instant it is thrown. b. Halfway to the top. c. At the top. d. As it nears the top. e. It is the same throughout the path.
c
Marcus Aurelius flies his F-35 Joint Strike Fighter plane at 475 m/s for 25 minutes. What distance does he travel in that time? a. 11,875 m b. 712,500 m c. 710,000 m d. 12,000 m
c
The difference between speed and velocity is that velocity is a measure of both speed and a. position b. acceleration c. direction d. time
c
Which of the following statements are true of the vertical motion of projectiles? a. The vertical component of a projectile's velocity is a constant value of 9.8 m/s. b. The vertical component of a projectile's velocity is constant. c. The vertical component of a projectile's velocity is changing. d. The vertical component of a projectile's velocity is changing at a constant rate. e. A projectile with an upward component of motion will have a upward component of acceleration. f. A projectile with an downward component of motion will have a downward component of acceleration. g. The magnitude of the vertical velocity of a projectile changes by 9.8 m/s each second. h. The vertical velocity of a projectile is 0 m/s at the peak of its trajectory. i. The vertical velocity of a projectile is unaffected by the horizontal velocity; these two components of motion are independent of each other. j. The final vertical velocity of a projectile is always equal to the initial vertical velocity. k. The vertical acceleration of a projectile is 0 m/s/s when it is at the peak of its trajectory. l. As a projectile rises towards the peak of its trajectory, the vertical acceleration will decrease; as it falls from the peak of its trajectory, its vertical acceleration will decrease. m. As a projectile rises towards the peak of its trajectory, the vertical acceleration is directed upward; as it falls from the peak of its trajectory, its vertical acceleration is directed downward. n. The peak height to which a projectile rises above the launch location is dependent upon the initial vertical velocity. o. As a projectile rises towards the peak of its trajectory, the vertical velocity will decrease; as it falls from the peak of its trajectory, its vertical velocity will decrease (becoming more negative).
c, d, f, g, h, i, n
A ball is thrown straight up, and takes 6 seconds to reach the peak of its trajectory. If air resistance is negligible, how long will it take for the ball to return to the height from which it was launched? a. less than 6 seconds b. impossible to say with the given information c. greater than 6 seconds d. 6 seconds
d
Which of the following descriptions of moving objects accurately portray a projectile? a. an object which is moving through the air and not touching any surface b. a falling skydiver with an open parachute c. any object upon which air resistance is negligible d. a free-falling object e. an object upon which the only significant force is the force of gravity f. a falling feather g. a falling feather in a vacuum chamber h. a falling feather in a falling vacuum chamber.
d, e, g, h
Which of the following statements are true of the horizontal motion of projectiles? a. A projectile does not have a horizontal velocity. b. A projectile with a rightward component of motion will have a rightward component of acceleration. c. The horizontal velocity of a projectile changes by 9.8 m/s each second. d. A projectile with a horizontal component of motion will have a constant horizontal velocity. e. The horizontal velocity of a projectile is 0 m/s at the peak of its trajectory. f. The horizontal velocity of a projectile is unaffected by the vertical velocity; these two components of motion are independent of each other. g. The horizontal displacement of a projectile is dependent upon the time of flight and the initial horizontal velocity. h. The final horizontal velocity of a projectile is always equal to the initial horizontal velocity. i. As a projectile rises towards the peak of its trajectory, the horizontal velocity will decrease; as it falls from the peak of its trajectory, its horizontal velocity will decrease. j. Consider a projectile launched from ground level at a fixed launch speed and a variable angle and landing at ground level. The horizontal displacement (i.e., the range) of the projectile will always increase as the angle of launch is increased from 0 degrees to 90 degrees. k. Consider a projectile launched from ground level at a fixed launch angle and a variable launch speed and landing at ground level. The horizontal displacement (i.e., the range) of the projectile will always increase as the launch speed is increased.
d, f, g, h, k
area under velocity vs. time
displacement
At what point in its path is the horizontal component of the velocity (vx) of a projectile the smallest? a. The instant it is thrown. b. Halfway to the top. c. At the top. d. As it nears the top. e. It is the same throughout the path.
e
A bullet is launched straight up with a velocity of 15 m/s. A feather is launched straight up with the same velocity of 15 m/s at the same time. Assume NO air resistance. Which of the following statements is true? i. The bullet reaches a higher maximum height than the feather ii. The bullet and the feather reach the same maximum height iii. The feather and the bullet hit the ground at the same time iv. The bullet will hit the ground with a greater speed than the feather
ii, iii
A skydiver jumps out of an airplane where air resistance is NOT negligible (cannot be ignored). She falls for a while before eventually hitting terminal velocity. The moment when she had the greatest acceleration was...
the moment she jumped out of the airplane
slope of position vs. time
velocity
