Question

A person brings amass of $1kg$ from infinity to a point A lnitially, the mass was at rest but it moves at a speed of $3m/s$ as it reaches A. The work done by the person on the mass is $-5.5J$ The gravitational potential at $A$ is

• A. $-1J/kg$
• B. $-4.5J/kg$
• C. $-5.5J/kg$
• D. $-10J/kg$

Answer 1

The correct option is D $-10J/kg$

Using work energy theorem:

$W_{person}+W_{gravity}=\Delta K.E.$

$-5.5+m(V_A-V_{infinity})=\frac{1}{2}m{v}^2-0=\frac{1}{2}\times 1\times 3^2$

$-5.5+V_A-0=4.5$

$V_A=10J/Kg$