I have heard the term backspinner in Cricket. What is a backspinner in Cricket? How does the bowler bowl a backspinner and who invented this type of delivery? Couldn't get much information on this type of delivery.
There is some info on wikipedia. To elaborate, a backspinner is a delivery that can be bowled by either a finger spinner or a wrist spinner and refers to any delivery in which the spin put on the ball is mainly in the 'back' direction, as opposed to a side spinner or topspinner. To be clear, the direction of spin is the same as how a ball rolling back towards the bowler would be rotating.
Many different bowlers, both finger and wrist spinners, have used different techniques to bowl backspinners over the years and these deliveries go by different names such as sliders, zooters, the teesra and some finger spinners 'arm ball' is basically a backspinner.
Like any spin bowler variation, the intention of a backspinner is deception. The bowler hopes the batsmen will player the ball as if it was a regular stock ball and be surprised to find it behaves differently. In the case of the backspinner, the ball will tend to land fuller than the batsmen expects and bounce off the pitch lower and quicker than they expect (hence the term 'slider', the ball 'slides' off the pitch instead of bouncing up). The reason for this has to do with some simple physics (that I won't go into) and contrasts with the usual flight of a spin bowlers delivery. Usually a regular side spinning stock ball will also be topspinning somewhat, so an offspin stock ball typically is spinning towards fine leg rather than square leg and an leg spinner towards the slips rather than point. Topspin makes the ball land shorter than it would otherwise, and causes it to grip onto the pitch bouncing slower and higher than otherwise. If the batsmen has been facing many of these stock balls from a bowler they may become used to that bounce and pace. If a bowler then bowls a backspinner they may be deceived by the fuller, lower bouncing ball. This may cause them to play over the ball and be bowled or given LBW.
The backspinner is not as well known as other variations, such as the googly, the doosra or the flipper probably because it is not a particularly spectacular ball. On its own it is not a particularly difficult ball to play, so a bowler wouldn't bowl it too often, but it get used as a less common variation to try and keep the batsmen uncertain about the bowler.
Shane Warne made a lot of fuss later in his career over the delivery he claimed to invent which he called the 'zooter'. However, it was simply a backspinner as had been bowled by many bowlers before him and was easier for him to bowl than his other variations once his shoulder had worn out from years of bowling.
A backspin ball tends to float through the air and kicks up when it bounces since it tends to kick backwards, causing the ball to slow down more than a ball without spin. The actual result depends on both the amount of spin and the angle of incidence. If a non-spinning ball is incident at an angle of about 20 degrees to the horizontal, then it will slide along the pitch until it bounces, at about 22 degrees to the horizontal. If the ball has backspin then the trajectory will probably be different. It depends on the ball speed and launch angle or on where the ball lands. In general, a ball with backspin landing at the same spot will be incident at a lower angle, say 18 degrees, and it will bounce up at about 20 degrees. But if the bowler sends down a slower backspin ball and if it lands at an angle of incidence of say 40 degrees, then the ball will start to slide along the pitch for a while and then grip the pitch before it bounces. This will cause the ball to slow down a lot during the bounce, so it will bounce up quite steeply, say at 50 degrees. The formula for the bounce angle is:
Slope of bounce angle = (vertical bounce speed) / (horizontal bounce speed)
where slope means the same thing as tangent in trigonometry. So, the effect of backspin or topspin depends on whether the ball slides throughout the bounce (as it does at low incident angles) or whether it gets a chance to grip the pitch, as it does at high angles of incidence.