Week 2 Homework Assignment

1. (P.55 Prob.10) A parked automobile slips out of gear, rolls unattended down a slight incline and then along a level road until it hits a stone wall. Draw a free-body diagram to show the forces acting on the car while it is in contact with the wall.
2. (P.55 Prob.14) A truck driving on a level highway is acted upon by the following forces: a downward gravitational force of 52kN (kilonewtons); an upward contact force due to the road of 52kN; another contact force due to the road of 7kN, directed east; and a drag force due to air resistance of 5kN, directed west. What is the net force acting on the truck?
3. (P.55 Prob.22) A spring scale in a French market is calibrated to show the mass of vegetables in grams and kilograms. (a) If the marks on the scale are 1.0mm apart for every 25grams, what maximum extension of the spring is required to measure up to 5.0kg? (b) What is the spring constant of the spring? [Remember that the scale really measure force.
4. (P.56 Prob.28) At what altitude above the Earth's surface would your weight be half of what it is at the Earth's surface? [Hint: See Problem 23.)
5. (P.56 Prob.36) A horse is trotting along pulling a sleigh through the snow. To move the sleigh, of mass m, straight ahead at a constant speed, the horse must pull with a force of magnitude T. (a) What is the net force acting on the sleigh? (b) What is the coefficient of kinetic friction between the sleigh and the snow?
6. (P.57 Prob.44) The coefficient of static friction between block A and a horizontal floor is 0.45 and the coefficient of static friction between block B and the floor is 0.30. The mass of each block is 2.0kg and they are connected together by a cord. (a) If a horizontal force F pulling on block B is slowly increased until it is barely enough to make the two blocks start moving, whaat is the magnitude of F at the instant that they start to slide? (b) What is the tension in the cord connecting blocks A and B at that same instant?
7. (P.58  Prob.52) A computer weighing 87N sits on the surface of your desk, The coefficient of friction between the computer and the desk is 0.60. (a) Draw a free-body diagram for the computer. (b) What is the magnitude of the frictional force acting on the compute? (c) How haard would you have to push on it to get it to start to slide across the desk?