20.0 kg block is being pushed forward on a flat surface with a force of magnitude 45.0 N against a frictional force of 13.0 N. (a) Draw a free-body diagram of the block.

 (b) What is the net force acting on the block? 
 (c) What is the change in kinetic energy after the force has pushed the block for 4.0 m? (d) How much work would it take to stop the block?

i need help with these two questions!

Object A is accelerated by exerting a 14-N force on it over a distance of 8.4 m. Object B is accelerated by exerting a 26-N force on it over a distance of 2.3 m. After the accelerations, how much more kinetic energy (in J) does object A have than object B?

The Super Sled travels with an initial kinetic energy of 3369 J horizontally and to the right along a frictionless flat surface, initially at a height of zero (initial gravitational potential energy = 0). The driver briefly engages the rocket over a distance (Ax) of 2.000 m, pushing the sled with a force of 400.0 N over that distance. The rocket is then turned off. The sled then goes up an inclined surface with a rough surface. The coefficient of kinetic friction on the incline is uk. At the top of the incline, the sled reaches a height h = 1.500 m above the ground where the surface becomes flat and frictionless again. The sled (including the rocket and driver) has a total mass of 87.00 kg. (Notes: assume that g = 9.810 m/s² , and that the mass of fuel used by the rocket is negligible. Do not use scientific notation). After &, rocket rocket Before propulsion propulsion starts ends rough inclined surface rocket frictionless engaged coefficient of kinetic friction = H surface h = 1.500 m…