For everyone asking about the ball question, here is what i did: For the first question to find the maximum height, the time was 6/20 because 20 was 1 second. And then use of equation s=ut+1/2at^2 because initial is zero as it falls from maximum height, all gpe no ke. You should get around 0.44m. Then for the second part, use the picture, if 0.44 was actual height, 6 cm was height on picture, that means total length(horizontal) was 9.3 cm. Convert both cm to meter. Use: If 6cm is 0.44m what is 9.3cm. You should get horizontal distance is 0.682m. Then use simple distance/time. Time for total should be 20/20 is 1 second and + 4/20 as it was 24 pictures and 20 was one second, so you need to add the extra 4, time should be 1.2. So velocity is 0.568m/s, atleast this is what i got, hopefully, it's correct.