Question

An object of mass $2kg$ is lifted vertically through a distance of $1.5m$. The work done in process is

• A. $29.4J$
• B. $19.4J$
• C. $17.4J$
• D. $20.4J$

Answer 1

The correct option is A $29.4J$

To lift a $2$kg object at constant speed,an upward force equal in magnitude to its weight,

$mg=2\times 9.8$N,must be exerted on the object.

The work done by this force is what we refer to as the work done against gravity :

Work against gravity $=mgh$

$=2\times 9.8$N$\times 1.5$m

$=19.6$N$\times 1.5$m

$=29.4‬$J