Why does my dad punch and kick me?

my mum and dad are divorced so every week i go to his for 2 nights, he always seems to want to hurt me consistently using aggression when talking to me. As im writing this im hiding in my bathroom crying because i tapped him and he pinned me on the floor and started smacking and punching my body calling me a slag and a little cunt. I told him if i does this anymore i'll call childline but he said if i do he will strangle me and im terrified to tell anyone.
Why does my dad punch and kick me?
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