What is the kinetic energy of an object with a mass of # 15 kg# that has been in freefall for # 7 s#?

1 Answer
Jan 26, 2016

Answer:

Assuming the object was stationary at the beginning of the 7 seconds, its velocity will be #68.6# #ms^-1# leading to a kinetic energy: #E_k# = #1/2mv^2 = 1/2*15*68.6^2=35,294.7 J=35.3 kJ#

Explanation:

Assuming that the initial velocity at #t=0# #s# is #u=0# #ms^-1#, the velocity, #v#, after #7# #s# will be:

#v=u+at=0+9.8*7=68.6# #ms^-1#

For an object of mass #m=15# #kg#, the kinetic energy is then given by:

#E_k=1/2mv^2=1/2*15*68.6^2=35,294.7 J=35.3 kJ#