*44.  A child operating a radio-controlled model car on a dock accidentally steers it off the edge. The car’s displacement 1.1 s after leaving the dock has a magnitude of 7.0 m. What is the car’s speed at the instant it drives off the edge of the dock?

 

Car leaves the dock with a horizontal only speed.  It gains vertical speed from gravity accelerating it downward.  We can find out how far the car has fallen by considering

 

 

Since there was no initial y velocity, we found the car has moved 5.93 m in the 1.1 s.  Now the total displacement can be found from

Since this forms a right triangle we have the relationship

 

Which can be used to find the horizontal displacement

 

 

Ignoring air resistance we have

 

Solving for initial velocity we get

 

 

 

 

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This page last updated on January 11, 2020