# Lift formula

1. Jun 2, 2010

### cmorency

What's the equation for the force of a lift. Drag formula is 1/2 ρ∆v^2 C A. And if you need the constant how would i determine the lift constant for a semi circle shape which spins sideways and has an acceleration of approximately 8.5 m/s down (should be gravity which is 9.8 ms/s). It is moving forward at an initial speed of 62.9 m/s if that helps.

2. Jun 3, 2010

### Staff: Mentor

Is the downward acceleration = 8.5 m/s2?

Lift is a force. If an object is in free fall without an opposing force, it would accelerate at g, assuming it's near sea level. If the object is accelerating downward with a rate less than 9.8 m/s2, then there must be an opposing force - drag or lift.

What is the significance of the diffrence between g and 8.5 m/s2?

3. Jun 3, 2010

### cmorency

Because one shape had a gravitational pull or downward acceleration of 11.5 m/s and one 8.5 and I'm attempting to calculate the force on both objects and why.

4. Jun 4, 2010

### RoyalCat

Try applying Newton's Second Law to the falling object.
You know that it is acted on by two forces, gravity and the lift force. Draw a free body diagram, and remember that $$\Sigma \vec F = m\vec a$$, the sum of all forces on a body is equal its mass times its acceleration. Knowing the acceleration, you can find what you're looking for.