a.)The object is at the origin at the times t=0 sec and t=6 sec.
b.)The object is at rest in the time intervals 2 < t < 4 sec and 7 < t < 9 seconds because in those time intervals the position is not changing.
c.)The velocity is constant and negative in the time interval 4 < t < 7 seconds because the position is decreasing with time.
d.)The position at t=2 secs is xf=4 m and at t=0 secs is xi=0 m. The time interval (delta_t) is 2 secs and the change in position (delta_x) = xf - xi = 4 m - 0 m = +4 m. Hence, the
average velocity= delta_x / delta_t = +4 m / 2 s = 2 m/s.
e.)The position at t=6 secs is xf=0 m and at t=0 secs is xi=0 m. The time interval (delta_t) is 6 secs and the change in position (delta_x) = xf - xi = 0 m - 0 m = +0 m. Hence, the
average velocity= delta_x / delta_t = +0 m / 6 s = 0 m/s.
a.)The points in the graph below represent the measured positions and times in the table. The solid line is a "smooth curve" through the points.
b.)The object is at rest in the time interval 0< t < 1 secs and near the time, t = 3.5 secs.
c.)The object is at the origin near the time, t = 2.5 secs, and again at the time, t = 5 secs.
d.)The position at t = 4 secs is xf = -1 m and at t = 2 secs is xi = +1 m. The time interval (delta_t) is 2 secs and, in that time interval, the change in position (delta_x) = xf - xi = -1 m - 1 m = -2 m. Hence, the
average velocity= delta_x / delta_t = -2 m / 2 s = -1 m/s.
a.)An object moves a distance of 25 meters in 3 seconds.
average speed= total distance / total time = 25 m / 3 sec = 8.3 m/s
b.)A train travels two kilometers, the first at an average speed of 50 km/hr and the second at an average speed of 100 km/hr.
The total distance = 25 km.
What is the total time?
First kilometer: time1 = 1 km / 50 km/hr = 0.02 hr
Second kilometer: time2 = 1 km / 100 km/hr = 0.01 hr
Hence, the total time to go 2 kilometers is time1 + time2 = 0.03 hr
For the entire trip,
average speed= total distance / total time
c.)A runner runs one kilometer in 3 minutes and a second kilometer in 4 minutes.
The total distance = 2 kilometers
The total time = 3 minutes + 4 minutes = 7 minutes
average speed= total distance / total time
d.)An object dropped from a height of 75 m strikes the ground in 4 seconds.
The total distance = 75 m
The total time = 4 s
average speed= total distance / total time
Return to P105 Course Schedule
Last updated: 6 Sep 1999
Comments: bland@indiana.edu