Question

A plane travels south for 120 km. The plane then travels north for 45 km.

If north is taken as the positive direction, what is the displacement of the plane?

a. 75 km
b. –75 km
c. 165 km
d. –165 km

Answer 1

b. -75

Explanation:

• It is already stated in the problem that north direction is positive. Hence, south is negative.
• We take 120km south to be -120km.
• Then, travelling north by 45km.
• We then add the two: -120km + 45km = -75km