No it’s simply that the man tried to slow that bridge down with the lever. The bridge being much heavier than him pushed and pulled him along, he tried to brace himself into the boards but to no avail.
It’s like travelling along an asphalt road at quite some speed, when you slam the brakes you’ll keep sliding along until you stop. The road doesn’t need to be slippy for that to occur.
I’m wondering if there isn’t a slight pitch or a grade that isnt obvious from this angle
No it’s simply that the man tried to slow that bridge down with the lever. The bridge being much heavier than him pushed and pulled him along, he tried to brace himself into the boards but to no avail.
It’s like travelling along an asphalt road at quite some speed, when you slam the brakes you’ll keep sliding along until you stop. The road doesn’t need to be slippy for that to occur.