A pick-up truck with two passengers weighs about 14000 N. In good driving conditions around a curve, the maximum friction with the road is equal to the truck's weight. What is the minimum safe curve radius that the truck could negotiate at 28.9 m/s

85.14 m

Explanation:

Let g = 9.81 m/s2. We can find the truck mass from its weight

m = W/g = 14000 / 9.81 = 1427 kg

So if the maximum friction could be the truck weight, which is F = 14000N, then that would also be the maximum centripetal force it could be. According to Newton 2nd law of motion, the maximum centripetal acceleration the truck can have when traveling at a curve is

a = F / m = 14000 / 1427 = 9.81 m/s2

By applying the following formula we can find the minimum safe radius R of the curve when traveling at speed of 28.9 m/s

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.