Newton's second law -- Crate sliding in the back of an accelerating truck

[PeroK]

I've used the simultaneous equations and i 've got for the acceleration ax= 0.39 m/s^2 and for the force of friction f= -880N
Is that right?

Sadly that doesn't look quite right. Did you remember the air resistance on the crate?

 

[Franklie001]

No you are right I've got for the acceleration ax=0.382 m/s^2
and for the friction force f = 944N

Am i right?

 

[Franklie001]

So if the friction force is 944N i have an equal and opposite friction force acting on the crate.
Therefore the second solution is given already Ff=944N.
And the coefficient is 0.043

 

[PeroK]

So if the friction force is 944N i have an equal and opposite friction force acting on the crate.
Therefore the second solution is given already Ff=944N.
And the coefficient is 0.043

I get a different answer. Did you remember the air resistance on the crate?

 

[Franklie001]

I've got Friction force = 1040N
and coefficient of kinetic friction u = 0.048

 

[Franklie001]

Yes i 've remembered everything this time

 

[Franklie001]

Seriously thanks for the big help on this one

 

[Steve4Physics]

I've got Friction force = 1040N
and coefficient of kinetic friction u = 0.048

Well done. But you may have a rounding error. I got the friction force to be 1027.45N which rounds to 1030N.