Question

Part 2: Finding Speed and Height Using Energy Directions: Use the KE and GPE equations to solve for speed or height depending on the situation. 1. A 1,000-kg car has 50,000 joules of kinetic energy. What is its speed? 2. A 200-kg boulder has 39,200 joules of gravitational potential energy. What height is it at?

Answer 1

1. A 1,000-kg car has 50,000 joules of kinetic energy. What is its speed?
KE = [1/2]m(v^2) => v = √[2KE/m] = √[2*50,000joules/1000kg] = 10m/s
2. A 200-kg boulder has 39,200 joules of gravitational potential energy. What height is it at? 
GPE = mgh => h = GPE / (mg) = 39,200 joules / (200kg * 9.8m/s^2) = 20m

3. A 1-kg model airplane has 12.5 joules of kinetic energy and 98 joules of gravitational potential energy. What is its speed? What is its height?
KE = [1/2]m(v^2) => v = √ [ 2KE/m] = √[2*12.5 j / 1kg] = 5 m/s
GPE = mgh => h = GPE/(mg) = 98/(1kg*9.8m/s^2) = 10 m

Answer 2

KE = [1/2]m(v^2) => v = √[2KE/m] = √[2*50,000joules/1000kg] = 10m/s2. A 200-kg boulder has 39,200 joules of gravitational potential energy. What height is it at? GPE = mgh => h = GPE / (mg) = 39,200 joules / (200kg * 9.8m/s^2) = 20m