Distance travelled in 4 hours...
730 - 442 = 288 miles
Speed for the 4 hours;
Speed = 288/4 = 72 miles/hour
Speed for the rest of 442 miles...;
(72 - 7) = 65 miles/hour
Time taken for 442 miles..
Time taken = Distance/Speed
; 442/65 = 6.8
Time taken = 6.8 hours
For each load, Work = (mass) x (gravity) x (distance .
Bigger load: Work = (10 kg) x (9.8 m/s²) x (2 m) = 196 joules .
Smaller load: Work = (5 kg) x (9.8 m/s²) x (4 m) = 196 joules.
The work required is equal in both cases.
The mass ratio of 2:1 is exactly balanced by
the height ratio of 1:2 .