Math Problem Statement

A uniform ladder of mass 8 kg and length 4 m is placed against a smooth wall, with its foot on rough horizontal ground, making an angle of 60° with the ground. A woman of mass 60 kg stands 1 m from the top of the ladder. The frictional force between the foot of the ladder and the ground is ____ N (3 s.f.)

Solution

This problem involves calculating the frictional force at the base of a ladder in static equilibrium. Let’s solve it step by step.


Given:

  1. Mass of the ladder: mladder=8kgm_{\text{ladder}} = 8 \, \text{kg}
  2. Length of the ladder: L=4mL = 4 \, \text{m}
  3. Mass of the woman: mwoman=60kgm_{\text{woman}} = 60 \, \text{kg}
  4. Distance of the woman from the top of the ladder: 1m1 \, \text{m}, so she stands 3m3 \, \text{m} from the bottom.
  5. Angle of the ladder with the ground: θ=60\theta = 60^\circ
  6. The wall is smooth, so there’s no friction at the wall.
  7. Gravitational acceleration: g=9.8m/s2g = 9.8 \, \text{m/s}^2

We need to find frictional force (FfrictionF_{\text{friction}}) at the base of the ladder.


Free Body Diagram and Forces:

  1. Weight of the ladder (WladderW_{\text{ladder}}): Wladder=mladderg=89.8=78.4NW_{\text{ladder}} = m_{\text{ladder}} \cdot g = 8 \cdot 9.8 = 78.4 \, \text{N} Acts at the midpoint of the ladder (2m2 \, \text{m} from the base).

  2. Weight of the woman (WwomanW_{\text{woman}}): Wwoman=mwomang=609.8=588NW_{\text{woman}} = m_{\text{woman}} \cdot g = 60 \cdot 9.8 = 588 \, \text{N} Acts 3m3 \, \text{m} from the base.

  3. Normal force at the base (NN): Acts vertically upward.

  4. Frictional force at the base (FfrictionF_{\text{friction}}): Acts horizontally to prevent the ladder from sliding.

  5. Reaction force at the wall (FwallF_{\text{wall}}): Acts horizontally.


Equilibrium Conditions:

  1. Vertical Force Balance: N=Wladder+WwomanN = W_{\text{ladder}} + W_{\text{woman}} [ N = 78.4 + 588 =

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Static Equilibrium
Torque
Forces in Equilibrium

Formulas

ΣF_x = 0 (Sum of horizontal forces is zero)
ΣF_y = 0 (Sum of vertical forces is zero)
Στ = 0 (Sum of torques is zero)

Theorems

Static Equilibrium Theorem

Suitable Grade Level

Grade 11-12