Question

Figure (3-E8) shows a 11.7 ft wide ditch with the approach roads at an angle of 15° with the horizontal. With what minimum speed should a motorbike be moving on the road so that it safely crosses the ditch ?Assume that the length of the bike is 5 ft, and it leaves the road when the front part runs out of the approach road.

Answer 1

To safely cross the ditch the motorbike should have a minimum range =11.7 ft + 5 ft =16.7 ft. 

Let the speed of the motorbike for this range be u.  θ =15°,  

Range x=(u² sin 2θ )/g  

=> 16.7 = (u² sin 30°)/32 

=> u² = 16.7*32*2  

=> u =√1068.8 = 32.7 ft/s  , is the minimum speed required to cross the ditch.

Answer 2

The required minimum speed of a bike will be