i need help with physic problem?

1.A person pushes horizontally with a force of 350 N on a 50 kg crate to move it across a level floor. The coefficient of kinetic friction between the crate and the floor is 0.50. Find the magnitude of the frictional force and the acceleration of the crate.

2.A block of mass 2.0 kg is pushed down on a vertically oriented spring that has a spring constant of 1500N/m.. Initially, the spring is compressed by 5.0 cm and the block is at rest. When the block is released, it accelerates upward. Find the speed of the block when the spring has returned to its equilibrium position.

3.The collision between a hammer and a nail can be considered to be approximately elastic. Assume that the nail, initially at rest, is struck by a 500-g hammer moving with an initial speed of 5.0 m/s. If the speed of the hammer is 4.6 m/s after the collision, calculate the following:

a.Kinetic energy of the nail after the collision

b.Momentum of the nail after the collision

c.The mass of the nail.