Word limit in post_content after more tag

I am using the following code to hide the teaser and show content only after more tag in loop:

<?php
$after_more = explode(
    '<!--more-->', 
    $post->post_content
); 
if( $after_more[1] ) { 
    echo $after_more[1]; 
} else {
    echo $after_more[0]; 
}
?>

Is there anyway to show only first 50 words instead of entire post content? I want to hide teaser and show 50 words after tag.