The gravtational field in a region is given by equation E= ( 5i+12j) N/kg . If a particle of mass 2kg is moved the change in gravitational potential energy is

Options

A. (-) 225 j
B. (-) 240 j
C. (-) 245 j
D. (-) 250 j

Answer

B

Explanation

dv=E.dr
dv=-`(5i=12j)(12i+5j) [ixxj=0,ixxi=i^2=1]`
-`(60+60) = -120`
The change in gravitational potential energy, u = mdv
`Rightarrow u= 2xx(-120) = - 240j`.