Impulse Graphs

Introduction

• In physics, impulse is defined as the product of average force and the time of contact during a collision. It plays a crucial role in understanding the effects of forces in a collision.
• Impulse can be represented graphically using force-time graphs, which provide valuable insights into the dynamics of a collision.

Force-Time Graph

• A force-time graph displays the force (in Newtons) on one axis and time (in milliseconds) on the other.
• The graph shows how the force applied to an object changes over the duration of a collision.
• The area under a force-time graph represents the impulse experienced by an object during the collision.

Peak Force vs. Average Force

• It's important to note that the peak force, which is the maximum force experienced during a collision, may be greater than the average force calculated for the entire collision.
• The peak force occurs at the point of maximum deformation or compression during the collision.

Impulse Calculation

• To calculate impulse from a force-time graph, simply find the area under the graph curve.
• Impulse (J) = Area under the force-time graph.
• Impulse is measured in Newton-seconds (Ns) or equivalently, kilogram-meter per second (kg·m/s).

Relationship Between Peak Force and Time of Contact

• In any collision with a fixed change in momentum (which means the change in momentum remains the same), the peak force experienced during the collision is inversely proportional to the time of contact.
• If the time of contact is increased, the peak force decreases, and vice versa.

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Impulse Graphs

Examples

Soft Squash Ball Collision:

• When a squash ball with a softer texture collides with a racquet, the force-time graph may show a longer time of contact, resulting in a lower peak force.
• The area under the graph remains the same, representing the same impulse.

Hard Squash Ball Collision:

• Conversely, when a harder squash ball collides with a racquet, the force-time graph may show a shorter time of contact, resulting in a higher peak force.
• Again, the area under the graph remains the same, indicating the same impulse.

Summary

• Impulse graphs display the relationship between force and time during a collision.
• The area under the graph represents the impulse experienced by an object during the collision.
• Peak force may differ from the average force, with peak force being inversely related to the time of contact.
• Understanding impulse and its graphical representation helps in analysing and optimising collisions in various scenarios.