Ch 10: Conservation of EnergyWorksheetSee all chapters

# Solving Projectile Motion Using Energy

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Sections
Intro to Conservation of Energy
Energy with Non-Conservative Forces
Conservative Forces & Inclined Planes
Motion Along Curved Paths
Energy in Connected Objects (Systems)
Solving Projectile Motion Using Energy
Escape Velocity
Springs & Elastic Potential Energy
Force & Potential Energy

Example #1: Projectile Motion with Energy

Transcript

Hey guys so in this video I want to talk about using the conservation of energy equation to solve projectile motion problems let's check it out. So it says your projectile motion problems asking for speeds or heights are easier to solve using conservation of energy equation, now they're not always easy to solve they're sometimes easy to solve and you can't always do this and I'll talk about this more at the end but we can use energy because speeds have to do with kinetic energy and heights have to do with potential energy so we're going to be able to in some cases use this equation which would be preferable because instead of having to pick one of the three or four equations of motion and have to worry about directions of positive or negative and all that kind of stuff and have to worry about decomposing vectors we can just instead use the energy in some cases to solve it all at once, alright?

Example #2: Projectile Motion with Energy

Transcript

Practice: You are practicing jumping as far as you can. In one attempt, you run and leave the floor with 7 m/s directed at an unknown angle. What maximum height do you reach if your speed at that point is 5 m/s? Ignore air resistance.

Practice: When you launch a 3-kg object from the ground with unknown initial speed directed at 37° above the x-axis, it hits the building shown below at 15 m above the ground with 25 m/s. Calculate the object’s launch speed. (Use g=10 m/s2.) Practice: A 3-kg box is nudged off the top of the path shown below, slides down, and is launched form the lower end of the path. The path is frictionless and its highest point is 10 m above the ground. The lower end is 2 m above the ground and makes 53° with the horizontal. Calculate the box’s speed:

(a) at the lowest point in the path;

(b) just before it leaves the path;

(c) at its highest point;

(d) just before it hits the ground. 