Calculating Relative Velocity of Grenade in Moving Vehicles

[anubis01]

Homework Statement

In an action-adventure film, the hero is supposed to throw a grenade from his car, which is going 91.0 km/h, to his enemy's car, which is going 106 km/h. The enemy's car is 14.5 m in front of the hero's when he let's go of the grenade.

a)If the hero throws the grenade so its initial velocity relative to him is at an angle of 45 above the horizontal, what should the magnitude of the initial velocity be?

b)Find the magnitude of the velocity relative to the earth.

Homework Equations

V_h/r=90 km/h
V_en/r=110 km/h
V_h/En=??

The Attempt at a Solution

a)I have no real idea on how to proceed with this problem. The real thing that is confusing me is the inclusion of the 14.5m and it can be used in calculating the initial velocity.

Any help is as always much appreciated.

 

[tiny-tim]

The real thing that is confusing me is the inclusion of the 14.5m and it can be used in calculating the initial velocity.

Hi anubis01!

You need to use x₁ for one car and x₂ for the other car, and x₁(0) = 0 while x₂(0) = 14.5.

 

[anubis01]

ah I see, I get it now. Thank you for the help.