```r
library(stringr)

physics %>% 
  filter(str_detect(text, "eq\\.")) %>% 
  select(text)
```

```
## # A tibble: 55 x 1
##    text                                                           
##    <chr>                                                          
##  1 "                         eq. 1: file eq01.gif"                
##  2 "                         eq. 2: file eq02.gif"                
##  3 "                         eq. 3: file eq03.gif"                
##  4 "                         eq. 4: file eq04.gif"                
##  5 "                       eq. 05a: file eq05a.gif"               
##  6 "                       eq. 05b: file eq05b.gif"               
##  7 the distance between the points being eq. 06 .                 
##  8 direction of its length with a velocity v is eq. 06 of a metre.
##  9 velocity v=c we should have eq. 06a ,                          
## 10 the rod as judged from K1 would have been eq. 06 ;             
## # ... with 45 more rows
```