8. as a roller coaster car crosses the top of a 51.0-m-diameter loop-the-loop, it's apparent weight is 1.80 times its true weight. what is the car's speed at the top? (the apparent weight is the same as the force of the tracks on the car)

The velocity at the top will be 26.4522 m/sec      

Explanation:

We have given

The diameter of the loop d = 48.01 m

Radius of the loop

The apparent weight at the top is given by

As the in question it is given that apparent weight is equal to 1.80 times of  the real weight

So the velocity at the top will be 26.4522 m/sec

im srry but ur wrong the answer is d a smooth rock, some red dirt, and an empty bird's nest.

initial speed when it is dropped is 150 ft/s

now at the same moment the acceleration due to gravity is perpendicular to its velocity

so as we know that

now we have centripetal acceleration a = 32 ft/s^2 as its perpendicular to velocity

while tangential acceleration at the same moment will be zero

so

now radius of curvature is given as

so the radius of curvature just after it is dropped is 703.125 ft