根据图中得出：d1=1.70cm，d2=2.90cm，d3=3.80cm，d4=4.50cm，d5=5.00cm．
根据运动学公式得：△x=at2，
a=
| △x |
| t2 |
| x5−x1 |
| 4t2 |
| d5−d4−d1 |
| 4t2 |
| 0.0500−0.0450−0.017 |
| 4×0.062 |
打点3时的速度：v3=
| x24 |
| 2t |
| d4−d2 |
| 2t |
| 0.045−0.029 |
| 2×0.06 |
答：小车的加速度大小为0.83m/s2，方向：向左，纸带上打下点3时小车的速度v3为0.13m/s．
| △x |
| t2 |
| x5−x1 |
| 4t2 |
| d5−d4−d1 |
| 4t2 |
| 0.0500−0.0450−0.017 |
| 4×0.062 |
| x24 |
| 2t |
| d4−d2 |
| 2t |
| 0.045−0.029 |
| 2×0.06 |