Practice calculating torque, applying rotational equilibrium, and modeling how loads are shared by bridge supports.
Read each problem carefully. Use appropriate units, show your setup, and explain your reasoning when asked.
Analyzing forces, moments, and support reactions in bridge structures
Physics - Grade 9-12
- 1
A 25 N force is applied perpendicular to a wrench 0.30 m from the bolt. Calculate the torque about the bolt.
- 2
A student pushes downward with 60 N on the end of a 0.80 m meter stick pivoted at the other end. The force makes a 90° angle with the stick. What is the torque about the pivot?
- 3
A 40 N force is applied to a door 0.75 m from the hinge, but the force is applied at an angle of 30° to the door surface. Calculate the torque about the hinge.
- 4
A uniform 6.0 m beam weighs 300 N and is supported at both ends. A 600 N person stands at the center of the beam. What upward force does each support provide?
- 5
A 10.0 m bridge beam is supported at both ends. A 1200 N car is parked 4.0 m from the left support. Ignore the weight of the beam. Find the upward force from the right support.
- 6
Using the bridge in Problem 5, find the upward force from the left support.
- 7
A 12.0 m uniform bridge beam weighs 2400 N and is supported at both ends. A 900 N load is placed 3.0 m from the left support. Find the upward force from the right support.
- 8
Using the bridge in Problem 7, find the upward force from the left support.
- 9
A seesaw is balanced on a pivot. A 500 N student sits 1.5 m to the left of the pivot. A second student sits 2.0 m to the right of the pivot. What must the second student's weight be for equilibrium?
- 10
A bridge sign hangs from a horizontal support arm. The 200 N sign is attached 1.2 m from the wall. A cable pulls upward at the end of the arm, 1.5 m from the wall. If the cable force is vertical, what force must the cable provide to keep the arm in rotational equilibrium? Ignore the weight of the arm.
- 11
A beam is in static equilibrium. What two conditions must be true for the beam to remain at rest without translating or rotating?
- 12
A 100 N force acts 0.50 m from a pivot. A 40 N force acts on the opposite side of the pivot. How far from the pivot must the 40 N force act to balance the torques?
- 13
A 16.0 m bridge is supported at both ends. A 2000 N truck is 6.0 m from the left support, and a 1000 N load is 12.0 m from the left support. Ignore the bridge weight. Find the upward force from the right support.
- 14
Using the bridge in Problem 13, find the upward force from the left support.
- 15
A bridge inspector notices that the right support force increases when a heavy truck moves closer to the right end of a bridge. Explain why this happens using torque and equilibrium.