Defining Key Terms in Movement Analysis
Let's break down these fundamental physics concepts that are crucial for understanding movement in sports and exercise.
Force
Force is the push or pull that causes an object to change its state of motion or shape. In sports, it's measured in Newtons (N).
ExampleA tennis player applying force to the ball during a serve, or a weightlifter pushing against a barbell are both examples of force in action.
Speed
- The rate of change of distance over time
- A scalar quantity (magnitude only)
- Formula: Speed = Distance / Time
- Measured in meters per second (m/s)
Velocity
- The rate of change of displacement over time
- A vector quantity (magnitude and direction)
- Formula: Velocity = Displacement / Time
- Also measured in m/s
Think of running around a track: Your speed might be 5 m/s, but if you end up where you started, your average velocity would be zero!
Displacement
- The straight-line distance and direction between start and end points
- A vector quantity
- Measured in meters (m)
Don't confuse displacement with distance! If you run 400m around a track, your distance is 400m, but your displacement is 0m if you finish where you started.
Acceleration
- The rate of change of velocity over time
- Formula: Acceleration = velocity / time
- Measured in meters per second squared (m/s²)
A sprinter accelerates from 0 to 10 m/s in 2 seconds: $a = \frac{10-0}{2} = 5$ m/s²
Momentum
- The product of mass and velocity
- Formula: Momentum = mass x velocity
- Measured in kilogram meters per second (kg⋅m/s)
Momentum is particularly important in contact sports like rugby, where the mass and velocity of players significantly impact collisions.
Impulse
- The product of force and time of application
- Equal to change in momentum
- Formula: Impulse = Force x momentum
- Measured in Newton-seconds (N⋅s)
Understanding impulse helps explain why landing on soft mats reduces injury - they increase the time of impact, reducing the force experienced.
HintWhen solving problems involving these concepts, always:
- Check your units
- Note whether you're dealing with vectors or scalars
- Consider the direction of movement
