- #1
hamza2095
- 28
- 1
Homework Statement
A ball that weights 1kg is thrown in the air, the hand being 1m above the ground. The velocity the ball was thrown at was 14m/s and it's maximum height was 6.5m above the ground. What is the efficiency for this energy transformation?
Homework Equations
Do I just get the mechanical energy of when the ball is in the hand (input) and the mechanical energy of when the ball reaches its maximum height (output) and use the standard efficiency equation (My attempt at the solution)? Or do I just act as if the hand is reference point and find the kinetic energy, then the gravitational potential energy (Using 5.5m because hand is 1m above ground) and find the efficiency that way
The Attempt at a Solution
EmBottom = m*g*h + 1/2 (mv^2)
= 1kg*9.8N/kg*1m + 1/2 (1kg(14m/s)^2)
= 107.8 J
EmTop = m*g*h (Just gravitational potential because the velocity at the top is 0, making the kinetic energy 0)
= 1kg*9.8*6.5m
= 63.7J
Efficiency = (output/input) * 100
= (63.7/107.8) * 100
= 59%