What is the kinetic energy of an object with a mass of #3 kg# that has been in freefall for #2 s#?

Question

What is the kinetic energy of an object with a mass of #3   kg# that has been in freefall for #2 s#?

Isabella Alvarez · Accepted Answer

E_k =600 J

from the first movument law #s= s° + v°t + 1/2 a t^2# but s°=0 and v° = 0 so #s= 1/2 a t^2= 1/2 10 m/s^2 (2s)^2 = 20 m# the kinetic energy is like the potential energy lost #E_w= mgh = 3kg xx 10 m/s^2 xx 20m = 600 J# #E_k= 600 J# otherwise you can have also #v= at= 10 m/s^2 xx 2 s = 20 m/s# #E_k =1/2 m xx v^2 = 1/2 xx 3 kg xx (20m/s)^2=600J#

Charlotte Aaron · Answer

undefined To calculate the kinetic energy of an object in freefall, you can use the equation:

$$ KE = \frac{1}{2} m v^2 $$

Where:
- $ KE $ is the kinetic energy.
- $ m $ is the mass of the object.
- $ v $ is the velocity of the object.

Since the object is in freefall for 2 seconds, its velocity after 2 seconds can be found using the equation:

$$ v = g \cdot t $$

Where:
- $ g $ is the acceleration due to gravity (approximately $ 9.8 \, \text{m/s}^2 $).
- $ t $ is the time in seconds (given as 2 seconds).

Now, you can substitute the values into the equation for kinetic energy and solve for $ KE $.