What is the kinetic energy of the object

[dg_5021]

Hey can someone check if i did it right please. Thanks




At t= 1.0 secs, a 0.40-kg object is falling with a speed of 6.0m/s. At t= 2.0 secs, it has a kinetic energy of 25J. (a) What is the kinetic energy of the object at t= 1.0 secs? (b) What is the speed of the object at t = 2.0 secs? (c) How much work was done on the object between t= 1.0 secs and t= 2.0 secs?

(a) k= (1/2)mv^2
=(1/2)(.40kg)(6.0m/s)^2
= 7.2J

(b) k= (1/2)mv^2
25J = (1/2)(.40kg)(m/s)^2
50J = (.40kg)(m/s)^2
=(125)^(1/2)
= 11.1803m/s

(c) w= (1/2)m11.2^2-(1/2)m6.0^2
=(1/2)m5.2^2
=(1/2)(.40kg)(5.2)^2
=5.36718J

 

[Pyrrhus]

The concept is fine, i didn't check arithmetic.

 

[M98Ranger]

Your calculations seem to be correct. Keep in mind that kinetic energy is dependent on the mass and velocity of the object, and it changes over time. Therefore, the kinetic energy at t=1.0 secs will not be the same as the kinetic energy at t=2.0 secs. Also, make sure to include units in your final answers. Overall, good job!