Question

A 40.0N force at an angle of 40.0° pulls a 5.00 kg block, itself attached to a spring (k = 30.0N/m). The
block and the surface have a kinetic friction coefficient of 0.200. Initially, the system is at rest and the
spring is at its natural length. When the block has moved 40.0 cm to the right, and using the work-energy
principle, find:

a) the thermal energy dissipated.

b) the work done by the external force.

c) the work done by the spring.

d) the final velocity of the block.

Answer 1

Solution-

Draw the FBD to get an understanding of the situation,

Substitute values for N

(a)

Thermal energy will be deciphered by the work done by friction,

x=0.4 m

Total thermal energy 1.944 J

(b)

Only X direction have the displacement so only x component will do the work,

x= 0.4 m

(c)

Work done by spring is given by,

(force opposite to displacement)

k= 30

x = 0.4 m

(d)

Use the equation of force in x-direction,

Substitute values for N

at x=0 v=0

Velocity at x=0.4 m

Final velocity at x=0.4 m is 1.6 m/s