Question #3994b

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Answer 1 · 2018-02-14T18:08:07

Acceleration of body #= F/m = "9.0 N"/"18.0 kg" = "0.5 m/s"^2#

A.
Distance covered in first 4 seconds

#S = ut + 1/2at^2#

#S = ("0 m/s" × "4 s") + (1/2 × "0.5 m/s"^2 × ("4 s")^2) = "4 m"#

Work done #= F × S = "9.0 N" × "4 m" = "36 Joules"#

B.
Distance covered in fourth second

#S = u + a(n - 1/2) = 0 + 0.5(4 - 1/2) = 7/4 "m"#

Work done #= F × S = "9.0 N" × 7/4"m" = 63/4 "Joules" = "15.75 Joules"#