Answer:
His initial velocity (speed) must be 64.16 m/s.
Explanation:
Horizontal Motion
When an object is horizontally launched at a speed v from a height h, the maximum horizontal distance (also called Range) traveled by the object can be calculated as follows:
[tex]\displaystyle d=v\cdot\sqrt{\frac {2h}{g}}[/tex]
Our daredevil is attempting to clear a river d=420 m wide with his motorcycle from a cliff h=210 m high. We need to find the speed needed to safely reach the opposite edge of the river.
From the above equation, we solve for v:
Speed:
[tex]\displaystyle v=d\cdot\sqrt{\frac {g}{2h}}[/tex]
[tex]\displaystyle v=420\cdot\sqrt{\frac {9.8}{2\cdot 210}}[/tex]
[tex]\displaystyle v=420\cdot\sqrt{\frac {9.8}{420}}[/tex]
v = 64.16 m/s
His initial velocity (speed) must be 64.16 m/s.
