A boy of mass 8kg falls from rest from a height of 100m, neglecting air resistance calculate his total energy after fallin down a distance of 40m
his total energy does not change
PE = 8*100
After 100m, it won't matter :-(
I dnt understand
8 * 9.8 * 100
Thanks, Damon. Forgot PE=mgh
Must have thought 8kg was his weight...
4800 J
Thanks for that
To calculate the total energy of the boy after falling down a distance of 40m, we need to consider potential energy and kinetic energy.
Potential Energy (PE) can be calculated using the formula:
PE = mass * gravitational acceleration * height
The gravitational acceleration (g) on Earth is approximately 9.8 m/s^2.
KE = (1/2) * mass * velocity^2
Given that the boy falls from rest, the initial velocity (u) is 0 m/s. Using the equation of motion:
v^2 = u^2 + 2ad
where v is the final velocity, u is the initial velocity, a is the acceleration (which is equal to g in this case), and d is the distance.
We can rearrange this equation to solve for the final velocity:
v = sqrt(u^2 + 2ad)
First, calculate the final velocity using the given distance of 40m:
v = sqrt(0^2 + 2 * 9.8 * 40) = sqrt(784) = 28 m/s
Now, calculate the total energy:
PE = 8 kg * 9.8 m/s^2 * 40 m = 3136 J
KE = (1/2) * 8 kg * (28 m/s)^2 = 6272 J
Total energy (E) is the sum of potential energy and kinetic energy:
E = PE + KE = 3136 J + 6272 J = 9408 J
Therefore, the total energy of the boy after falling down a distance of 40m is 9408 J.