A block of mass 4 kilograms is initially moving at 5m/s on a horizontal surface. There is friction between the block and the surface which causes the block to come to a complete stop. The coefficient of kinetic friction between the block and the surface is 0.5. If the system is defined as the block only, which of the following statements would be correct? A. There is a negative change in internal energy of the system as the block comes to a stop
B. There is a positive change in internal energy of the system as the block comes to a stop
C. There is a negative work done to the system as the block comes to a stop
D. There is a positive work done to the system as the block comes to a stop

Ahollow metal sphere has 6 cm and 11 cm inner and outer radii, respectively. the surface charge density on the inside surface is −100nc/m2. the surface charge density on the exterior surface is:

Three different objects, all with different masses, are initially at rest at the bottom of a set of steps. each step is of uniform height . the mass of each object is a multiple of the base mass : object 1 has mass 4..00m , object 2 has mass 1..96m , and object 3 has mass . when the objects are at the bottom of the steps, define the total gravitational potential energy of the three-object system to be zero. if the objects are then relocated as shown, what is the new total potential energy of the system? each answer requires the numerical coefficient to an algebraic expression. each algebraic expression is given using some combination of the variables , , and , where is the acceleration due to gravity. enter only the numerical coefficient. (example: if the answer is 1..23mgd , just enter 1.23)

For which pair of objects would adding the same a