4.6. A block of mass 20kg is at rest on a rough horizontal ground.
The coefficient of friction between the block and the ground is 0.3. A
horizontal force F is applied steadily to the block according to the
law: F=ť - t + 4, F is in newtons and t is the time in seconds
Calculate the time it takes the block to start moving. What is the
speed of the block when t = 4.Os.

Suppose that a mass of 2 kg is attached a spring whose spring constant is 50. the system is damped such that b = 12 . the mass is set in motion with an initial velocity of -8 m/s at a position 0 meters from equilibrium. set up and solve a differential equation that models this motion. write your solution in the form a cos ( ω t − α ) where α is a positive number. use your solution to fill in the information below: what is the amplitude of the motion? what is the value of ω ? what is the phase shift?