reaction time
A student is testing her reaction time by trying to keep a light bulb on for exactly 5 s by matching a stopwatch. When she turns the light bulb off, the stopwatch reads 5.13 s. What is her reaction time?
.13 seconds
What would you due for a measurement of a mass in physics?
kg
A baseball pitcher throws a fastball at 44 m/s. If the batter is 20 m from the pitcher, approximately how much time does it take for the ball to reach the batter?
v=d/t
v=44
d=20
meter/sec
20/44=.4545 or .45 sec
An automobile is going 20 m/s when it applies the brakes and stops after traveling a distance of 20 m. If the automobile was going at 10 m/s, it would be able to stop in a distance of
When the speed is cut in half, the braking distance becomes one fourth, or 5 m.
A student is spinning a turntable with a wooden block resting on it. The block is located 10 cm from the center of the table, and the turntable is rotating 15 times every minute. What is the speed of the wooden block on the turntable?
The speed of the spinning block is given by v = d t, where d is the circumference. The circumference = 2 π r = 2(3.14) × (10 cm) = 62.8 cm. The time it takes the block to rotate around the table, covering a distance equal to the circumference is derived from the rotations/minute - 60 s for 15 rotations means 4 s for 1 rotation. To find the speed, v = d t = (62.8 cm) (4 s) = 15.7 cm/s.
A race car driver is being tested for reaction time. In several practice trials, the driver’s reaction time was recorded as 0.15 s, 0.20 s and 0.25 s. What was the driver’s average reaction time?
0.20
Three students measure the length of their classroom and get the following values: Student A – 8.54 m Student B – 8.57 m Student C – 8.52 m
Because all three students received three different measurements, this is an example of
random error
Give the defining equation for acceleration in words, and by using symbols.
Acceleration is the change in velocity with respect to a change in time and is represented using the following symbols:
a=∆v ∆t.
What is an important consideration in determining the width of the GO Zone for a yellow light?
the width of the intersection, time of the yellow light, and your velocity
The force that holds the wooden block on the turntable while it is spinning is provided by the force of
Friction
Two students are having a contest to see who has the quickest reaction time. A third student gives them both stopwatches that were started at the same time and tells them to stop them when he says stop. The student with the quickest reaction time will have the stopwatch with the
lowest time
You are driving on a highway that posts a 65 mi/h (105 km/h) speed limit. The speedometer is accurate within 5 mi/h (8 km/h).
What speed should you drive as shown on the speedometer to guarantee that you will not exceed the speed limit?
60 mi/h might really be 65 mi/h, so to be safe, you should drive 60 mi/h.
What does the slope of a velocity- time graph represent?
The of the velocity-time graph represents the change in velocity with respect to time (acceleration).
what is important to consider in your stop zone
velocity, reaction time, and negative acceleration
force is
push or pull
What can slow down your reaction time driving?
Alchol, changing radio stations, talking on cell phone
You are driving on a highway that posts a 65 mi/h (105 km/h) speed limit. The speedometer is accurate within 5 mi/h (8 km/h).
What could a passenger in the vehicle do while you are driving to estimate how accurate the speedometer is? (Hint: The road has mile markers, and the passenger has a wristwatch that shows seconds.)
The passenger may watch the mile markers and mark the time when they are passed. A driver traveling at 60 mi/h would travel 1 mi in 60 s (60 mi/h is 60 mi in 60 min), so if the vehicle is traveling 60 mi/h, the next mile marker should be passed in exactly 60 s.
If an automobile’s velocity changes from 55 m/s to 45 m/s in 2 s, then what is its acceleration?
The acceleration is given by a = ∆v ∆t . The velocity changes from 55 to 45 (a change of 10 m/s) and the time change is 2 s, giving an acceleration of
– 5 m/s2.
what is the overlap zone
where the go zone overlaps with the stop zone
centripetal force
is the force directed towards the center of a object that keeps it in a circular path
What is reaction time
the time it takes to respond to a situation.
An automobile travels between the 200-m and 350-m markers on a highway in 10 s. The average speed of the automobile during this interval is
15 m/s
in a distance time graph a straight line means
stopping
An automobile is approaching an intersection with a yellow light. The automobile is traveling with a velocity of 20 m/s, and goes a distance of 15 m before the driver starts to apply the brakes. What would be the automobile’s rate of negative acceleration if it comes to a stop in 50 m?
The distance traveled during the reaction time of the driver is given by d = vtr. To obtain tr , the distance traveled is divided by the automobile’s speed, giving (15 m) (20 m/s) = 0.75 s .
centripetal acceleration
change in direction of the velocity with respect to time