Question

Question #53757

Jed was driving his car at 40km/hr on a subdivision where the speed limit is 20km /hr. He was spotted by an officer in a motorcycle, who accelerates in pursuit. By the time jed sees the officers motorcycle it was traveling at 60km/ hr. What is the officer's velocity relative to jed car.

Expert's answer

Answer on Question #53757, Physics / Mechanics | Kinematics | Dynamics

Jed was driving his car at 40km/hr on a subdivision where the speed limit is 20km/hr. He was spotted by an officer in a motorcycle, who accelerates in pursuit. By the time Jed sees the officer's motorcycle it was traveling at 60km/hr. What is the officer's velocity relative to Jed car.

Solution:

If two objects are moving in parallel their relative velocity can be calculated.

If two objects move in same direction at different speeds we will have:

If speed of 1st object = x km/hr and Speed of 2nd object = y km/hr

Therefore, their relative speed = $(x - y) \text{ km/hr} [x > y]$ , then in our case

\text{relative speed} = 60 - 40 = 20 \text{ km/hr}

Answer. $20 \text{ km/hr}$

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Comments

Aleo

28.07.15, 15:14

When asking about relative velocity, all that means is the perceived velocity of the policeman by Jed. Since Jed is traveling at 40km/hr and the policeman is traveling at 60km/hr relative to the earth, the policeman's relative velocity to Jed is: 60km/hr - 40km/hr = 20km/hr. The policeman is traveling at 20km/hr relative to Jed.