Chapter 4 Sample problems A) Determine if the problem is equilibrium or non-equilibrium, B) Set-up the problem. C) Solve the problem. 1) A force of 7.50 N pushes three boxes with masses from back to front of 1.30 kg, 3.20 kg, and 4.90 kg. Find the contact forces between boxes 1 and 2. and the contact force between boxes 2 and 3. 2) A catcher stops a 48.5 m/s pitch in his glove, bringing it to rest in 0.15 m. If the force exerted by the catcher is 803 N, what is the mass of the ball? 3) A 17.0 kg child rides on a 2.30 kg sled pulled by his mother and father. Both pull with a force of 55.0 N at an angle of 35 degrees on either side of the forward direction. What is the acceleration of the child? 4) A 25.25 kg crate is on a plane inclined at 30 above the horizon. What Force is required to keep it at rest? 5) The current in a river pushes a 6125 kg barge with a force of 4125 N downstream South. Two ropes on either side of the river hold the barge in place. If one rope makes an angle 55 North of East with a size of 3255 N. Find the angle and force (Tension) supplied by the other rope. Friction: Setup and solve. 1) What force is required to move a 2535 kg crate along a horizontal surface with u = 0.0250? 2) A 17.25 kg crate is on a plane inclined at 25. What is the minimum force required to push the crate up the plane if the coefficient of kinetic friction is 0.875? 3) You want to nail a 1.3 kg board onto the wall of a barn. To position the board before nailing, you push it against the wall with a horizontal force F to keep it from sliding to the ground. If the coefficient of static friction between the board and the wall is 0.860, what is the least force you can apply and still hold in place