## Tuesday, 23 September 2014

### Friction, Inclined Planes Problems

Question 1
 The system below is in equilibrium. Frictional forces can be neglected. a) Given that m2 = 0·2kg, calculate m1. b) Calculate the gravitational potential energy gained by m1 if m2 is pushed down 0·3m. c) If m1 is removed and replaced by an object of mass 2m1, calculate the acceleration of the system. d) Calculate the total kinetic energy of the system after 2s of acceleration (with the mass 2m1 in place and assuming that vo = 0).
Question 2
 A body rests, without slipping, on a plane which is inclined at 30° to the horizontal. a) Draw a diagram showing the forces acting on the body. b) If the body has a mass of 2kg, calculate the magnitude of the force of friction acting on it.
Question 3
 An object of mass m = 5kg is being pulled up an inclined plane which is at 40° to the horizontal. The object is pulled at a constant speed of 0·8ms-1 by a force which acts parallel to the inclined plane. The coefficient of friction between the object and the plane is 0·2. a) Draw a diagram showing the forces acting on the object. b) Calculate the magnitude of the force of friction acting on the object. c) Calculate the gain in g.p.e. when the object has moved 0·5m (measured parallel to the slope). d) Calculate the total work done in pulling the block 0·5m (measured parallel to the slope).