Tony smashed the gas pedal, the van shot forward, and Jack was jolted back in his seat by the abrupt acceleration.
托尼猛踩油门，维修车一下蹿了出去，突然的加速让杰克的身体紧贴在椅背上。
2
If an arm is stretched forward under water resistance is increased and a reaction force back ward is developed both of which would contribute to negative acceleration.
如果手臂在水中是向前伸展则阻力会随之增加而向后方的反作用力也会出现，二者都会产生负加速度。
3
And a kind acceleration starting curve with trapezoid is put forward.