Aperture and shutter speed and focal length

These pictures were taken using Nikon D5000.I have not used any tripod or any flash.I had always used the aperture priority in taking most of the photos.I have now realised that I need to use a tripod when I am using a smallest apertuter to avoid any camera shake and thus resulting in picture blurring.

 This picture was taken with a shutter speed 0.400 seconds a fairly fast shutter, but still some of the vehicles are blurred.So to get a clearer picture one should use the fastest speed, like 1/1000.

This picture was taken with a shutter speed of 0.760, still slower than the first picture and most of the vehicles are blurred

This picture was taken with a focal length of 18 mm.The picture contains a lot of nearer and far objects.

This picture was taken with an apertureF 4 and the nearest object the swan is clearer than the distant trees

 This image was taken with an aperture F13 and the distant trees are a bit more clearer

This picture was taken with an aperture F25.the nearer object is clear as well as the distant trees.There is a good depth of field. This shows that smaller the aperture greater the depth of field.This is really useful in taking landscape pictures. Again to get the good depth of field one has to use the smallest aperture which results in camera shake and there will be blurring of the picture.to avoid this blurring one has to use a tripod. if you see this picture very carefully the distant trees are a bit blurred.This will be clearly seen if the picture is enlarged. I need to use a tripod in future to take landscape images.