B. picking up a box off the floor
Answer:
Explanation:
Let acceleration of fall be a .
v² = u² + 2as
v = 3.8 m /s
u = 0
s = 3.5 m
3.8² = 0 + 2 x a x 3.5
a = 2.06 m /s²
Since this acceleration is less than g , an upward force is acting on the firefighter in the form of friction . Let this force be F . Let mass of the firefighter be m .
m = 765 / 9.8
= 78.06 kg
mg - F = ma
765 - F = 78.06 x 2.06
765 - F = 160.8
F = 604.2 N .
I think that they are called meteorites
Newton's second law is stated as:
F=ma,
a = (7-4)/1.5 = 2 m/s^2 (it is a deceleration due to impact with floor. And thus the ball exerts force on the floor).
Therefore,
F= 0.3*2 = 0.6 N
