- #1

helppls

## Homework Statement

*Tower bridge in London is an example of a bascule bridge (moveable bridge) where each part that is raised up is called a ‘span’. In this photo, the two spans are raised to an angle of 38° to let two tug boats through. Each span is 30.5 m long and weighs 1 x 108 kg (you can assume that the mass is distributed evenly).*

a) Calculate the force required to raise one span to an angle of 38°

b) How does this force change if a span is raised to an angle of 85°?

a) Calculate the force required to raise one span to an angle of 38°

b) How does this force change if a span is raised to an angle of 85°?

I know that the center of gravity is at 15.25 m , which should then be the distance R

the bridge weighs 9.8*10^8 N

## Homework Equations

torque = r*F

torque = r*F*sin(theta)

## The Attempt at a Solution

a) the torque, I think, is

15.25 * (9.8 x 10^8) *sin(38) = 9.2 x 10^9 Nm ... but I don't know how to find the force required?

b) I am assuming that the force required lessens as you increase the angle of the bridge. I'm stuck.