Monster trucks can launch several meters into the air because their suspension systems are built to handle huge changes in position, speed, and force. Suspension travel is the distance a wheel can move up and down relative to the truck frame. Large travel gives the truck more time and distance to slow down during a landing.
This matters because reducing the stopping force protects the driver, chassis, tires, and shock absorbers.
Key Facts
- Suspension travel is the vertical distance a wheel can move between full extension and full compression.
- Work-energy relation for landing: Favg d = 1/2 m v^2, so more stopping distance d lowers the average force.
- Impulse relation: Favg Δt = m Δv, so a longer stopping time Δt lowers the average force.
- Gravitational potential energy at jump height h is PE = mgh.
- A stiffer spring has a larger spring constant k, and spring force follows F = kx.
- Shock absorbers convert motion energy into heat by damping, which reduces bouncing after impact.
Vocabulary
- Suspension travel
- The maximum distance a wheel can move up and down relative to the vehicle frame.
- Shock absorber
- A damping device that resists rapid suspension motion and converts mechanical energy into heat.
- Spring constant
- A measure of spring stiffness, defined by how much force is needed for a given compression or stretch.
- Impulse
- The change in momentum caused by a force acting over a period of time.
- Center of mass
- The average location of an object's mass, which helps determine how it moves and rotates in the air.
Common Mistakes to Avoid
- Thinking bigger tires alone make landings safe. Tires help absorb impact, but the suspension and shocks provide most of the controlled stopping distance.
- Using only jump height to predict landing force. Landing force depends on speed, mass, suspension travel, damping, and how quickly the truck is brought to rest.
- Assuming stiff suspension is always better. If the suspension is too stiff, it stops the truck over a shorter distance and can create larger impact forces.
- Ignoring rotation during big air. A truck can land nose-first or tail-first if torque changes its angle, which can overload part of the suspension.
Practice Questions
- 1 A 5400 kg monster truck lands with a vertical speed of 8.0 m/s. If the suspension compresses 1.2 m while stopping the downward motion, estimate the average upward force using Favg d = 1/2 m v^2.
- 2 A truck reaches a peak height of 4.5 m above the landing point. Ignoring air resistance, what is its vertical speed just before landing using v = sqrt(2gh) with g = 9.8 m/s^2?
- 3 A monster truck with long suspension travel and strong damping lands smoothly, while a similar truck with short travel bounces high after landing. Explain which energy transfers are different in the two landings.