physic- free fall?

Question

Ball bearings are made by letting spherical drops of molten metal fall inside a tall tower -- called a shot tower -- and solidify as they fall.
(a) If a bearing needs 4.0 s to solidify enough for impact, how high must the tower be?

(b) What is the bearing's impact velocity? (Take up to be positive.)

Cokey · Accepted Answer

So here are your givens:
t = 4 s.
Vi = 0 m/s
a = 9.81 m/s^2

You will use this formula:
d = Vi*t + 1/2*a*t^2

Now fill in the data we know.

d = 4(0) + .5*4^2*9.81

d = 78.48

We now have the displacement, at 78.48 meters.

Getting the final velocity before impact will require a simple formula:
Vf = Vi + a*t

Vf = 0 + 9.81*4

Vf = 39.24 m/s

And there we have your final velocity.

Doctor Q · Answer

A) distance = 1/2 * acceleration due to gravity * time^2

distance = 1/2 * 9.81 * 4^2 = 1/2 * 9.81 * 16 = 78.48 metres.

B) Final Velocity = Initial Velocity + (Acceleration * Time)

Final Velocity = 0 + 9.81 * 4 = 39.24 ms^-1

This will be Negative is you are taking up to be positive.

appleton_strings · Answer

a) Use s = ut + 1/2 a t^2

u = 0, as the bearing is falling from rest; a = g, acceleration is due to gravity; t = 4 (given).

Then s = 1/2 * g * 4^2 = 8*g = 78.45m


b) Use v = u + at

u = 0, (again); a = g (again); t = 4 (again).

Then v = g * 4 = -39.23m/s

(the - indicates that the bearing is moving downwards).

lily · Answer

can anyone tell what is the correct answer for this question?

physic- free fall?

4 Answers