Ball not rolling properly CSS - html

Question

My animation works quite nicely but it seems its slipping and doesn't seem to roll. What could be the problem?
FIDDLE HERE : http://jsfiddle.net/erkoda3m/2/
img {
height: 150px;
width: 150px;
animation: roll 4s linear infinite;
-webkit-animation: roll 4s linear infinite;
}
#-webkit-keyframes roll {
0% {
-webkit-transform: translateX(0px) rotate(0deg);
}
50% {
-webkit-transform: translateX(300px) rotate(360deg);
}
100% {
-webkit-transform: translateX(0px) rotate(0deg);
}
}
#keyframes roll {
0% {
transform: translateX(0px) rotate(0deg);
}
50% {
transform: translateX(300px) rotate(360deg);
}
100% {
transform: translateX(0px) rotate(0deg);
}
}
<img src="http://i.imgur.com/5NvOwB5.png">

Answer 1

The diameter is 150px, so circumference will be 150π = 471.24px. So if the rotation angle is 360°, translateX value will be circumference of the ball, or 471.24px :
img {
height: 150px;
width: 150px;
animation: roll 4s linear infinite;
-webkit-animation: roll 4s linear infinite;
}
#-webkit-keyframes roll {
0% {
-webkit-transform: translateX(0px) rotate(0deg);
}
50% {
-webkit-transform: translateX(471.24px) rotate(360deg);
}
100% {
-webkit-transform: translateX(0px) rotate(0deg);
}
}
#keyframes roll {
0% {
transform: translateX(0px) rotate(0deg);
}
50% {
transform: translateX(471.24px) rotate(360deg);
}
100% {
transform: translateX(0px) rotate(0deg);
}
}
<img src="http://i.imgur.com/5NvOwB5.png">
If you want to keep translateX constant and change rotate value, instead, you can calculate the angle by (400/471.24)*360 = 305.57deg
img {
height: 150px;
width: 150px;
animation: roll 4s linear infinite;
-webkit-animation: roll 4s linear infinite;
}
#-webkit-keyframes roll {
0% {
-webkit-transform: translateX(0px) rotate(0deg);
}
50% {
-webkit-transform: translateX(400px) rotate(305.57deg);
}
100% {
-webkit-transform: translateX(0px) rotate(0deg);
}
}
#keyframes roll {
0% {
transform: translateX(0px) rotate(0deg);
}
50% {
transform: translateX(400px) rotate(305.57deg);
}
100% {
transform: translateX(0px) rotate(0deg);
}
}
<img src="http://i.imgur.com/5NvOwB5.png">