The 5 kg
block strikes a spring which has resistance of F_{s} = k_{s},
where k = 900N/m2, with v = 7m/s. Calculate the velocity of the block after
it has compressed the spring by 0.4m. 1) 4.49 m/s. 2) 3.45 m/s. 3) 2.56 m/s. 4) 7.54 m/s 

The spring
force does negative work.The normal reaction and the weight do not contribute
to the work. The energy work equation for the system is given by, This is the velocity of the block at the time it compresses the spring by 0.4m. 