A 20 kg block is released from rest from the top of a ramp at point A at a construction site as shown in the diagram. The ramp is inclined at an
angle of 30° to the horizontal and its top is at a height of 5 mabove the ground.

6.2 the kinetic frictional force between the 20kg block and the surface of the ramp is 30N. use energy principles to calculate the:

a. work done by the kinetic frictional force.
b. speed of the block at the point B at the bottom of the ramp​

Answer///air resistance,drag;

W= fd
where f is an applied force and d is the distance over which it is applied. when a parachuting skydiver is at constant velocity, he is experiencing "terminal velocity", the point at which his acceleration down is canceled out by air resistance. that means that the resisting force of the air is equal to his weight, but in the opposite direction. with this, we can solve for the work done by the force.
w = fd
w = (92.0)(9.81 m/s^2) (325)
w= 2.93 x 10^5 j
the value for work in this case is positive because it is pushing up on the skydiver, who has a downward force of gravity.
therefore the answer is 2.93 x 10^5 j

Year  1936,  lehman predicted that the earths 'inner core' is solid. she observed that the seismic signals during her study were bent and did not pass through instead bouncing back. later it was confirmed that the earth's inner core was solid made up of nickel-iron and had a molten outer core.