Question

A frog is sitting on a lily pad when it sees a delicious fly. He darts out his tongue at a speed of 4.10 m/s to catch the fly. The tongue has a mass of 0.410 g, and the rest of the frog plus the lily pad have a mass of 13.0 g. What is the recoil speed of the frog and the lily pad? Ignore drag forces on the pad due to the water.

Answer 1

Given:

Initial velocity = 4.10 m/s

Mass of tongue, = 0.410 g

Mass of the rest of frog, = 13.0 g

Let's find the recoil speed of the frog and the lily pad.

Apply the Law of Conservation of Momentum:

$v(m_1+m_2)=m_Tv_T$

Rewrite the formula for v:

$v=\frac{m_Tv_T}{m_1+m_T}$

Where:

mT is the mass of tongue = 0.410g = 0.000410 kg

vT = 4.10 m/s

m1 = 13.0 g = 0.013 kg

Hence, we have:

$\begin{gathered} v=\frac{0.410\times4.10}{13.0+0.410} \\ \\ v=0.125\text{ m/s}\approx0.13\text{ m/s} \end{gathered}$

Therefore, the recoil speed of the frog and lily pad is 0.13 m/s

ANSWER:

0.13 m/s