9702 AS Physics for CIE Prepared by Faisal Jaffer

AS Physics Assignment # 3b Date : Q1)1 A horizontal force of 490N is required to slide sledge of mass 600 kg over a flat surface. Calculate the coefficient of friction. What is the unit of coefficient of fiction? (ans: .083 units). Q2)2 A force of 98N is just able to move a body of weighing 45kg on a rough horizontal surface. Calculate the coefficient for fiction and the angle of friction. (ans: 0.22 units and angle 77.48o) Q3)3 A woman at an airport is towing her 20 kg suitcase at constant speed by pulling on a strap at an angle of θ above the horizontal. She pulls on the strap with a 35 N force, and the frictional force on the suitcase is 20 N. (a) Draw a free body diagram of the suitcase. (b) What angle does the strap make with the horizontal? (ans: 55.15o ) (c) What normal force does the ground exert on the suitcase? (ans: 167.5N) Q4)4 A racing car accelerates uniformly from 0 to 80 km/h in 8 s. The magnitude of the force that accelerates the car is approximately equal to the magnitude of the frictional force between the tires and the road. Determine the minimum coefficient of static friction between the tires and the road. (ans: 0.29)

1 Satish Gupta, Physics for Grade 11, page no 219 2 Satish Gupta, Physics for Grade 11, page no 223 3 http://electron9.phys.utk.edu/phys135d/modules/m5/Friction.htm 4 http://electron9.phys.utk.edu/phys135d/modules/m5/Friction.htm