What is the kinetic energy of an object with a mass of # 5 kg# that has been in freefall for # 2 s#?

Question

What is the kinetic energy of an object with a mass of #  5   kg# that has been in freefall for # 2 s#?

Charles Aeschliman · Accepted Answer

960.4 J

The formula of Kinetic energy is #1/2mv^2# where m is mass and v is velocity. This simply means that a mass m moving with a velocity v has kinetic energy #1/2mv^2#. We know mass, so lets find velocity. It is given that it has been falling for two seconds. So its velocity # = a times t# .In this case the acceleration is caused due to gravity and hence acceleration is 9.8 meters per second squared. Plugging it into the equation, if it has been falling for 2 seconds, then its velocity is #9.8 times 2 = 19.6# meters per second Now since we have velocity, we can find Kinetic energy by simply putting the values of mass and velocity in the first equation K.E.=#1/2 times 5 times 19.6^2#= 960.4 J

Benjamin Asiedu · Answer

#960.4# joules

Well, kinetic energy is defined through the equation, #"KE"=1/2mv^2# #m# is the mass of the object in kilograms #v# is the velocity of the object in meters per second The velocity of the free-fall object is defined through the equation, #v=u+at# #u# is the initial velocity #a# is the acceleration of the object #t# is the time in seconds In this case, #a=g=9.8 \ "m/s"^2#, assuming air resistance is negligible. If the object was dropped from something, then #u=0#, and so: #v=0+9.8 \ "m/s"^2*2 \ "s"# #=19.6 \ "m/s"# Therefore, the kinetic energy is: #"KE"=1/2*5 \ "kg"*(19.6 \ "m/s")^2# #=2.5 \ "kg"*384.16 \ "m"^2"/s"^2# #=960.4 \ "kg m"^2"/s"^2# #=960.4 \ "J"#

William Audy · Answer

undefined The kinetic energy of the object is 98.1 joules.