Question

Arthur and Betty start walking toward each other when they are 100 m apart. Arthur has a speed of 3.0 m/s and Betty has a speed of 2.0 m/s. Their dog, Spot, starts from Arthur's side at the same time and runs back and forth between them. By the time Arthur and Betty meet, what is Spot's displacement?

Answer 1

60 m

Step-by-step explanation:

Arthur and Betty will be walking for the same amount of time t

Speed of Arthur = 3 m/s

Speed of Betty = 2 m/s

Distance = Speed × time

Distance covered by Arthur = 3t

Distance covered by Betty = 2t

Distance that Arthur and Betty will cover will be 100 m

3t+2t = 100

⇒5t = 100

⇒t = 100/5

⇒t = 20 s

So, Arthur and Betty will be walking for 20 seconds

Spot is by Arthur's side and keeps running in between them until they meet. So, Spot will be running for 20 seconds and the displacement covered will be the distance covered by Arthur which is

3t = 3×20 = 60m

Displacement is the shortest distance between two points so, Spot's displacement will be 60 m