Question

Starting from rest, a 1.8 x 10^-4 kg flea springs straight upward. While the flea is pushing off from the ground, the ground exerts an average upward force of 0.42 N on it. This force does +2.7 x 10^-4 J of work on the flea. (a) What is the flea's speed when it leaves the ground? (b) How far upward does the flea move while it is pushing off? Ignore both air resistance and the flea's weight.

Answer 1

Answer:

a)

1.73 m/s

b)

6.43 x 10⁻⁴ m

Explanation:

m = mass of the flea = 1.8 x 10⁻⁴ kg

v₀ = initial speed of the flea = 0 m/s

v = final speed of the flea

W = work done by the force on the flea = 2.7 x 10⁻⁴ J

Using work-change in kinetic energy, Work done is given as

W = (0.5) m (v² - v₀²)

Inserting the values

2.7 x 10⁻⁴ = (0.5) (1.8 x 10⁻⁴) (v² - 0²)

v = 1.73 m/s

b)

d = distance moved by the flea while pushing off

F = Upward force applied on the flea by ground = 0.42 N

Work done is also given as

W = F d

2.7 x 10⁻⁴ = (0.42) d

d = 6.43 x 10⁻⁴ m