There is not a doubt that there is a gender gap in most STEM fields, especially in physics. Australian academics have put forward an interesting theory about the gender divide in physics and hypothesise that it is because of "boys' fondness for urinating at targets." Due to this hobby, boys are able to understand force, momentum, fluid dynamics, and other key concepts of physics better. Although they cannot prove this theory without empirical evidence, they think that this "self directed, hands-on, intrinsically (and sometimes extrinsically and socially) rewarding activity must have a huge potential contribution to learning, resulting in a deep, embodied, material knowledge of projectile motion that's simply not accessible to girls."
They argue that physics is a difficult subject for girls because they lack the experience of grasping projectile motion first hand. It is usually taught in the beginning of physics courses because it is a relatable concept, like throwing a ball. Since boys stand up and have "playful urination practices," they may have an advantage over girls in understanding physics. They do offer more traditional explanations for the gender gap, like the problem of society associating logical and mathematical ways of thinking with masculinity, and some parents or teachers may inadvertently discourage girls from pursuing STEM subjects.
This study started because in the UK, 1/5 students who studies "A-level" physics is a girl. When conducting this study, they found the differences were pronounced when asking questions about projectile motion that focused on the velocity of objects that are thrown, kicked, or fired. In order to combat this gender gap, specialists have suggested changing the curriculum so that forces and momentum are not taught first, and to put a slighter emphasis on projectile motion. They don't suggest that girls also start "playful urination practices" but they do start with subjects like energy conservation, which they claim is more central to physics.