A worker lifts a 40 kg heavy box from the ground and puts it on the horizontal frictionaless surface table 1.5 m high from the ground. Then he pushes the box on the table. The velocity of the box changes from 5 m/s to 2 m/s?
A) find the work done in lifting the box up from the ground to the top of the table.
B) find the work done in moving the box across the table.
C) find the total work done by the worker.
A) find the work done in lifting the box up from the ground to the top of the table.
B) find the work done in moving the box across the table.
C) find the total work done by the worker.
1 Answer
Jan 28, 2018
A) Work done in lifting the box from the ground to the top of the table
#"W"_1 = "mgh" = "40 kg" × "9.8 m/s"^2 × "1.5 m" = "588 J"#
B) Work done in moving the box across the table.
#"W"_2 = 1/2"m"("v"^2 - "u"^2) = 1/2 × "40 kg" × [("5 m/s")^2 - ("2 m/s")^2] = "420 J"#
C) Total work done by the worker.
#"W"_"Total" = "W"_1 + "W"_2 = "588 J + 420 J" = "1008 J" = "1.008 kJ"#
