Physics 1 homework question

Question

Chameleons catch insects with their tongues, which they can rapidly extend to great lengths. In a typical strike, the chameleon's tongue accelerates at a remarkable 220 m/s2 for 20 ms , then travels at constant speed for another 30 ms .

During this total time of 50 msms, 1/20 of a second, how far does the tongue reach?

Answer 1

Lauren,

We have here 2 stages:

1. t₁=20ms of a motion with constant acceleration a=220 m/s² with zero starting velocity
2. t₂=30ms of a motion with the constant velocity v₁=at₁ achieved at the end of the 1st stage

So, the tongue's displacement during the 1st stage would be

Δx₁=at₁²/2=1/2*(220 m/s²)*(20/1000)²s²=0.044m

At the end of the 1st stage the tongue would achieve a velocity of v₁=at₁=220 m/s² * (20/1000)s=4.4m/s

Then, traveling with that velocity for 30ms, the tong would get further displaced by

Δx₂=v₁*t₂=(4.4m/s)*(30/1000)s=0.132m So, the total displacement of the chameleons' tongue becomes

Δx=Δx₁+Δx₂=0.044m+0.132m=0.176m