An object moves from x = -2.1 m, y = 3.7 m, z = 1.4 m to x = 3.3 m, y = -1.1 m, z = 4.2 m in a time of 5.3 s.What is its average velocity?
A)(0.23 m/s) + (0.49 m/s) + (0.53 m/s)
B)(5.4 m/s) − (4.8 m/s) + (2.8 m/s)
C)(1.0 m/s) − (0.91 m/s) + (0.53 m/s)
D)(1.0 m/s) + (0.91 m/s) + (1.1 m/s)
E)−(1.0 m/s) + (0.91 m/s) + (0.53 m/s)

Question

An object moves from x = -2.1 m, y = 3.7 m, z = 1.4 m to x = 3.3 m, y = -1.1 m, z = 4.2 m in a time of 5.3 s.What is its average velocity?
A)(0.23 m/s) + (0.49 m/s) + (0.53 m/s) 
B)(5.4 m/s) − (4.8 m/s) + (2.8 m/s) 
C)(1.0 m/s) − (0.91 m/s) + (0.53 m/s) 
D)(1.0 m/s) + (0.91 m/s) + (1.1 m/s) 
E)−(1.0 m/s) + (0.91 m/s) + (0.53 m/s)

Quizplus · Accepted Answer

Average velocity is the displacement divided by the elapsed time. The final position vector minus the initial position vector gives the displacement vector.

Displacement vector = (3.3-(-2.1))i + (-1.1-3.7)j + (4.2-1.4)k 
= 5.4i - 4.8j + 2.8k

Elapsed time = 5.3 s

Average velocity = Displacement vector / elapsed time 
= (5.4/5.3)i - (4.8/5.3)j + (2.8/5.3)k 
= 1.0i - 0.91j + 0.53k

Therefore, the correct choice is C, which represents the average velocity vector as 1.0 m/s eastward (i-direction), 0.91 m/s southward (j-direction), and 0.53 m/s upward (k-direction).

An Object Moves from X = -2