Impulse problem (intro mechanics)

[acherentia]

Homework Statement

A rubber ball (mass 0.26 kg) is dropped from a height of 1.7 m onto the floor. Just after bouncing from the floor, the ball has a speed of 3.6 m/s.
(a) What is the magnitude and direction of the impulse imparted by the floor to the ball? Magnitude ? kg · m/s

(b) If the average force of the floor on the ball is 17 N, how long is the ball in contact with the floor?

Homework Equations

dp=Fdt=m(vf-vi)

The Attempt at a Solution

a)the unknown is the initial speed of the dropping ball under free fall:

v_i= sqrt (2 x 9.8 x 1.7) = 5.8

delta p= 0.26 (3.6--5.8)=2.4

b) dt=dp/F_ave=0.14 s

Please let me know what is wrong here, my electronic assignment system is telling me the numbers are wrong. Thank you!

 

[ideasrule]

Your answers all seem right to me.