Log Fume Acceleration, Velocity, and change in mass

[spoogiest]

Currently working on a high school physics assignment.
I need help on some questions, just so that I know I am in the right direction. I am not here to get you guys to do my homework for me. But anyway, the following questions are about a log fume ride, and the acceleration and velocity of a boat going down a slope.

Homework Statement

1. The first question asks to work out the acceleration. (Force = 2450N, Mass = 500KG)
2. The second question asks for the velocity. (Time for the boat to reach bottom = 2.96s)
3. The third question asks if a change of mass would affect the acceleration and velocity.

Homework Equations

f=ma
a=change in V/t

The Attempt at a Solution

1. For question 1, I simply used the f=ma equation, finding a. a=f/m, a=2450/500, a=4.9m/s forwards. I assume this is correct.
2. The second question, I used the acceleration formula to work out the change in velocity. change in velocity = 4.9 x 2.6, therefore velocity = 14.504m/s or 52.214km/h. However the real answer is given, being 58km/h. Is there any reason why I am quite a bit off? or am I using the wrong equation.
3. For the third question, I know physics says that everything falls at the same rate no matter what the mass, but after doing a few sample calculations changing the mass around in each case, the acceleration and velocity for each are always different. Am I going wrong anywhere?

Anyway, any help is greatly appreciated.

Thanks :)

 

[spoogiest]

Forgot to mention, there is no friction, and the ride falls with gravity.

Thanks