Final answer:
The reaction force to a kangaroo's jump is the force exerted by the ground on the kangaroo, which is equal in magnitude and opposite in direction to the action force the kangaroo applies to the ground.
Step-by-step explanation:
The Reaction Force to a Kangaroo's Jump
When a kangaroo jumps, the action force exerted by the kangaroo acts on the ground. According to Newton's third law of motion, every action has an equal and opposite reaction. Therefore, the reaction force in this case would be the force exerted by the ground on the kangaroo. This reaction force is equal in magnitude and opposite in direction to the action force applied by the kangaroo. It is important to note that this force is not lesser nor greater than the action force but is exactly equal to it. Additionally, kangaroos make use of a bending motion in their legs to reduce the impact of the force, thereby cushioning the shock of landing.