A block with a mass of 4 kg is sliding across a horizontal surface with an initial speed of 5 m/s. Because of kinetic friction, the energy of this system will decrease linearly with the distance traveled by the block.
What is the average power (in W) supplied by the force of kinetic friction acting on the block if the block moves 4 m before coming to a stop?

What is the momentum of a 2 kg object moving at 15 meters per second

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 the car in the picture ,in which direction is the normal force? -into the screen -down -out of the screen -up