How to load all the products under one category in magento?.

If we want to load all the products under one category we need to use below code is the simplest way,

 $cat_id = 5;
 $collection = Mage::getModel("catalog/product")->getCollection();
 $_category =  Mage::getModel("catalog/category")->load($cat_id);    
 $collection->addCategoryFilter($_category);