Ten joules of work are done in accelerating a 2.0- kilogram mass from rest across a horizontal,?

Question

frictionless table. The total kinetic energy gained by the mass is

a. 3.2 J
b. 5.0 J
c. 10. J
d. 20. J

Answer 1

W = F*S = M*a*S = 2*a*S = 10 .... (1)

vf^2 - vi^2 = 2*a*s

vi=0, and from (1)

vf^2 = 10 ...

so, KE = 1/2*M*vf^2 = 1/2*2*10 = 10 J

Quick Check: If there is no potential energy (vertical change) then the total work done is always equals to KE.

Answer 2

An easy way to look at it is that 10J work has been done on the body. There is no loss of energy since the table is frictionless, therefore the mass must have acquired 10J kinetic energy, whatever its mass.