3 |
2 |
根据v=
s |
t |
小红上学时上坡的时间:t1=
| ||
v |
2s |
5v |
小红上学时下坡的时间:t2=
| ||
|
2s |
5v |
且t1+t2=36min,即
2s |
5v |
2s |
5v |
s |
v |
小红放学时上坡的时间:t3=
| ||
v |
3s |
5v |
小红放学时下坡的时间:t4=
| ||
|
4s |
15v |
小红放学的时间t=t3+t4=
3s |
5v |
4s |
15v |
13s |
15v |
13 |
15 |
s |
v |
13 |
15 |
答:小红放学回家要走的时间为39min.
2 |
5 |
2 |
3 |
3 |
2 |
s |
t |
| ||
v |
2s |
5v |
| ||
|
2s |
5v |
2s |
5v |
2s |
5v |
s |
v |
| ||
v |
3s |
5v |
| ||
|
4s |
15v |
3s |
5v |
4s |
15v |
13s |
15v |
13 |
15 |
s |
v |
13 |
15 |