Projectile motion graphs | Two-dimensional motion | AP Physics 1 | Khan Academy

Khan Academy
26 Mar 201807:41

Summary

TLDRThis educational video script explores the physics of projectile motion on Earth, ignoring air resistance. It discusses the acceleration, velocity, and position in both the y (vertical) and x (horizontal) directions for three different scenarios: throwing a projectile straight out, at an angle downwards, and straight downwards. The script emphasizes that while acceleration due to gravity is constant and downward in the y direction, there is no acceleration in the x direction. The velocity and position graphs for each scenario are described, highlighting how to treat the x and y components independently.

Takeaways

  • 🌍 In all scenarios, the acceleration in the y-direction is constant and downward due to gravity, represented as -g.
  • 🚀 There is no acceleration in the x-direction for any scenario, assuming no air resistance.
  • 📉 The velocity in the y-direction decreases at a constant rate due to gravity for all scenarios, regardless of the initial velocity vector.
  • 🔄 The velocity in the x-direction remains constant for all scenarios since there is no acceleration in this direction.
  • 🔵 For the first scenario, the projectile has a positive initial y-velocity, which decreases over time until it reaches zero at the peak of its trajectory.
  • 🔵 In the x-direction for the first scenario, the projectile moves at a constant positive velocity, leading to a linear increase in position.
  • 🔵 The blue scenario starts with zero initial y-velocity, accelerating downward over time, while the x-velocity is slightly higher than the first scenario.
  • 🟡 In the third scenario, the projectile has a negative initial y-velocity, which continues to decrease, and the x-velocity is similar to the blue scenario.
  • 📊 The position versus time graph for the y-direction shows an initial increase followed by a decrease, while in the x-direction, it shows a constant rate of increase.
  • 📚 Once the initial velocity is broken down into x and y components, each component can be analyzed independently in terms of motion.

Q & A

  • What is the acceleration in the vertical (y) direction for a projectile launched on Earth?

    -The acceleration in the vertical direction is constant and due to gravity, which is directed downwards. It is represented as negative g, where g is the acceleration due to gravity.

  • Is there any acceleration in the horizontal (x) direction for a projectile on Earth, assuming no air resistance?

    -No, there is no acceleration in the horizontal direction. The acceleration remains at zero, assuming no air resistance.

  • How does the initial velocity vector of a projectile affect its acceleration due to gravity?

    -The direction in which the projectile is thrown does not affect the acceleration due to gravity. The acceleration due to gravity is always constant and directed downwards.

  • What is the initial velocity in the y direction for a projectile thrown straight out from a cliff?

    -The initial velocity in the y direction for a projectile thrown straight out is positive, as it is launched upwards.

  • How does the velocity in the y direction change over time for a projectile thrown straight out?

    -The velocity in the y direction starts positive and decreases at a constant rate due to the constant negative acceleration caused by gravity.

  • What is the initial velocity in the x direction for a projectile thrown straight out?

    -The initial velocity in the x direction is positive and remains constant over time, assuming no air resistance.

  • What happens to the velocity in the y direction for a projectile thrown at an angle downwards?

    -For a projectile thrown at an angle downwards, the initial velocity in the y direction is negative and becomes more negative over time due to gravity.

  • How does the velocity in the x direction compare between the scenarios of throwing the projectile straight out and at an angle downwards?

    -The velocity in the x direction remains constant for both scenarios, assuming no air resistance, but the magnitude may differ based on the initial throw.

  • What is the position-time graph like for a projectile thrown straight out in the y direction?

    -The position-time graph for a projectile thrown straight out in the y direction will show an initial increase followed by a decrease as the projectile reaches its peak and then falls back down.

  • How does the position in the x direction change for a projectile thrown straight out from a cliff?

    -The position in the x direction increases at a constant rate as the projectile moves horizontally with a constant velocity.

  • What is the key takeaway from analyzing the motion of a projectile in both the x and y directions?

    -The key takeaway is that once the initial velocity is broken down into x and y components, each component can be treated independently. The motion in one direction does not affect the motion in the other direction.

Outlines

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Keywords

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Highlights

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Transcripts

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Ähnliche Tags
PhysicsProjectile MotionGravityMotion AnalysisEducationalScienceAccelerationVelocityPositionTwo-Dimensional
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