Another Newton's Law Question.

1. Dec 7, 2004

scan

Question: A force of 50N acting at 37degrees above the horizontal pulss a block along the floor with constant velocity. If the coefficient of friction between the blocck and the floor is 0.2, what is the mass of the block?

the answer in the book is 23.4kg

but when I did it I got 20.3kg.

my friend did it and he got 23.4kg but when I use his calcutions and calculated out I get 23.5kg.

He says you have to take the Normal force and substract 50sin37 because its being pulled along that direction. I say do you don't.

Help?

2. Dec 7, 2004

Staff: Mentor

That is correct.
The fact that the 50N force is applied at angle will definitely affect the normal force. Write down the equilibrium equations for both horizontal and vertical components. Combine the two equations and you can solve for the mass.

3. Dec 7, 2004

scan

oh ok. that makes sense now. its just the textbook is so bad that it doesnt' say that the normal force can be affected.