Answer: 4.8 s
Explanation:
We have the following data:
[tex]m=180 kg[/tex] the mass of the raft
[tex]F=75 N[/tex] the force applied by Sawyer
[tex]V=2 m/s[/tex] the raft's final speed
[tex]V_{o}=0 m/s[/tex] the raft's initial speed (assuming it starts from rest)
We have to find the time [tex]t[/tex]
Well, according to Newton's second law of motion we have:
[tex]F=m.a[/tex] (1)
Where [tex]a[/tex] is the acceleration, which can be expressed as:
[tex]a=\frac{\Delta V}{\Delta t}=\frac{V-V_{o}}{t-t_{o}}[/tex] (2)
Substituting (2) in (1):
[tex]F=m\frac{V-V_{o}}{t-t_{o}}[/tex] (3)
Where [tex]t_{o}=0[/tex]
Isolating [tex]t[/tex] from (3):
[tex]t=\frac{m(V-V_{o})}{F}[/tex] (4)
[tex]t=\frac{180 kg(2 m/s-0 m/s)}{75 N}[/tex]
Finally:
[tex]t=4.8 s[/tex]
