High-speed photos of a 190 ?g flea jumping vertically show that the jump lasts 1
ID: 1647167 • Letter: H
Question
High-speed photos of a 190 ?g flea jumping vertically show that the jump lasts 1.2 ms and involves an average vertical acceleration of 120 g .
Part A
What average force does the ground exert on the flea during its jump?
Express your answer to two significant figures and include the appropriate units.
Part B
What impulse does the ground exert on the flea during its jump?
Express your answer to two significant figures and include the appropriate units.
ANSWER: J = ?
Part C
What's the change in the flea's momentum during its jump?
Express your answer to two significant figures and include the appropriate units.
Explanation / Answer
m = 190g = 190x10-6g = 1.90x10-7 kg
t = 1.2 ms = 1.5 x10-3 s
Abar = average acceleration = 120g = 120 * 9.81m/s2 = 1177m/s2
(1) Fbar = m * Abar = 1.90x10-7 kg * 1177 = 2.23x10-4 N =2.23x10-4 kg m/s2
(2)Impulse I = Fbar * t = 2.23x10-4 N * 1.5 x10-3 s= 3.34x10-7 N ·s= 3.34x10-7 kg m s1
Impulse is also given by:
(3) I = p
Therefore, p = 3.34x10-7 N ·s=3.34x10-7 kg m s1