Starting from rest, a 2.3x10-4 kg flea springs straight upward. While the flea is pushing off from the ground, the ground exerts an average upward force of 0.49 N on it. This force does 3.6x10-4 J of work on the flea. (a) What is the flea's speed when it leaves the ground

3.13 m/s

Explanation:

From the question,

Since the flea spring started from rest,

Ek = W ... Equation 1

Where Ek = Kinetic Energy of the flea spring, W = work done on the flea spring.

But,

Ek = 1/2mv² ... Equation 2

Where m = mass of the flea spring, v = flea's speed when it leaves the ground.

substitute equation 2 into equation 1

1/2mv² = W ... Equation 3

make v the subject of the equation

v = √ (2W/m) ... Equation 4

Given: W = 3.6*10⁻⁴ J, m = 2.3*10⁻⁴ kg

Substitute into equation 4

v = √[2*3.6*10⁻⁴) / 2.3*10⁻⁴]

v = 7.2/2.3

v = 3.13 m/s

Hence the flea's speed when it leaves the ground = 3.13 m/s