press b to ragdoll

local UserInputService = game:GetService("UserInputService")
local Players = game:GetService("Players")

local player = Players.LocalPlayer

local function getRoot(char)
    return char and char:FindFirstChild("HumanoidRootPart")
end

local function trip()
    if player and player.Character and player.Character:FindFirstChildOfClass("Humanoid") and getRoot(player.Character) then
        local hum = player.Character:FindFirstChildOfClass("Humanoid")
        local root = getRoot(player.Character)

        hum:ChangeState(Enum.HumanoidStateType.Physics) -- make player ragdoll
        root.Velocity = root.CFrame.LookVector * 35 -- push force

        -- Stand back up after 2 seconds
        task.wait(2)
        hum:ChangeState(Enum.HumanoidStateType.GettingUp) -- Get back up
    end
end

UserInputService.InputBegan:Connect(function(input, gameProcessed)
    if gameProcessed then return end -- prevent exec if ui is focused

    if input.KeyCode == Enum.KeyCode.B then -- change key
        trip()
    end
end)