Explanation of the difference between scalar and vector quantities and methods of measurement of these quantities is covered in Stage 1, Topic 1: Linear motion and forces.
This subtopic uses the concept of acceleration developed in Stage 1, Subtopic 1.1: Motion under constant acceleration.
Uniformly accelerated motion is described in terms of relationships between measurable scalar and vector quantities, including displacement, speed, velocity, and acceleration.
Motion under constant acceleration can be described quantitatively using the three motion equations.
- Solve problems using the constant acceleration formulae.
Projectile motion can be analysed quantitatively by treating the horizontal and vertical components of the motion independently.
- Construct, identify, and label displacement, velocity, and acceleration vectors.
- Resolve velocity into vertical and horizontal components.
- Use vector addition and trigonometric calculations to determine the magnitude and direction of the velocity of a projectile at any moment of time.
An object experiences a constant gravitational force near the surface of the Earth, which causes it to undergo uniform acceleration.
- Explain that, in the absence of air resistance, the horizontal component of the velocity is constant.
The motion formulae are used to calculate measurable quantities for objects undergoing projectile motion.
- Calculate the time of flight when a projectile is launched horizontally.
- Calculate the time of flight and the maximum height for a projectile when the launch height is the same as the landing height.
- Calculate the horizontal range of a projectile when it is launched horizontally or when the launch height is the same as the landing height (or the flight time is given).
- Determine the velocity of a projectile at any time using trigonometric calculations or vector addition.
- Explain qualitatively that the maximum range occurs at a launch angle of 45° for projectiles that land at the same height from which they were launched.
- Describe the relationship between launch angles that result in the same range.
- Describe and explain the effect of launch height, speed, and angle on the time of flight and the maximum range of a projectile.
- Analyse multi-image representations of projectile paths.
When a body moves through a medium such as air, the body experiences a drag force that opposes the motion of the body.
- Explain the effects of speed, cross-sectional area, and density of the medium on the drag force on a moving body.
- Explain that terminal velocity occurs when the magnitude of the drag force results in zero net force on the moving body.
- Describe situations such as skydiving and the maximum speed of racing cars where terminal velocity is achieved.
- Describe and explain the effects of air resistance on the vertical and horizontal components of the velocity, maximum height, and range of a projectile.
- Describe and explain the effects of air resistance on the time for a projectile to reach the maximum height or to fall from the maximum height.