If a child ran into the road 65 to 70 feet ahead of your vehicle, what is the highest speed from which you could stop with good brakes before hitting him? 30 mph 50 mph 40 mph 20 mph

The highest speed from which you could stop the vehical with good brakes before hitting him is 40 mph. Therefore the correct option ia c) 40mph.

Given :

Stopping Distance range - (65ft , 70ft)

Solution :

We know that the stopping distance (d) is,

  --- (1)

Where,

v = speed of the vehicle.

= 0.8, coefficient of static friction under good road conditions.

---    (acceleration due to gravity)

Now at d = 65 ft

put the values of v, g and in equation (1) we get,

v = 57.87 ft/sec = 39.5 mph

Now at d = 70 ft

Put the values of v, g and in equation (1) we get,

v = 60.05 ft/sec = 40.9 mph

So the safe speed is 39.5 mph approximately 40 mph. Therefore the correct option is c) 40 mph.

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real, smaller and upside-down.   so the answer should be b.