Final answer:
The length of a jump can be increased by increasing horizontal velocity because horizontal and vertical motions are independent; the object will cover more ground before landing since the time of fall is dictated solely by the vertical motion.
Step-by-step explanation:
The length of a jump can be increased by increasing the horizontal velocity while keeping the vertical velocity the same because the horizontal and vertical motions of a projectile are independent. According to physics principles, once an object is in motion, its horizontal velocity remains constant if there is no horizontal force acting upon it, such as air resistance in an ideal scenario. This means it will continue to move horizontally at the same speed. As the vertical motion is only influenced by gravity, which acts downwards and does not affect the horizontal motion, increasing the horizontal velocity will cause the object to travel further before it hits the ground. This is because the time it takes for the object to fall to the ground (affected only by vertical velocity and gravity) remains the same regardless of the object's horizontal velocity.