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/s^2 for 20 msms, then travels at constant speed for another 30 ms. Required:
During this total time of 50 ms, 1/20 of a second, how far does the tongue reach?

Solution :

We know,

Distance,

For the first 20 ms,

S = 0.044 m

In the remaining 30 ms, it has constant velocity.

v = 4.4 m/s

Therefore,

S' = 0.132 m

So, the required distance is = S + S'

                                              = 0.044 + 0.132

                                              = 0.176 m

Therefore, the tongue can reach = 0.176 m or 17.6 cm

The total distance is 0.176 m.

Explanation:

For t = 0 s to t = 20 ms

initial velocity, u = 0

acceleration, a = 220 m/s^2

time, t = 20 ms

Let the final speed is v.

Use first equation of motion

v = u + at

v = 0 + 220 x 0.02 = 4.4 m/s

Let the distance is s.

Use second equation of motion

Now the distance is

s' = v x t

s' = 4.4 x 0.03 = 0.132 m

The total distance is

S = s + s' = 0.044 + 0.132 = 0.176 m

we need to know the time interval during which the force acts. impulse of force = momentum change

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.