14.0 m uniform ladder weighing 490 N rests against a frictionless wall. The ladder makes a 65.0°-angle with the horizontal. (a) Find the horizontal and vertical forces (in N) the ground exerts on the base of the ladder when an 850-N firefighter has climbed 4.10 m along the ladder from the bottom. horizontal

Respuesta :

Answer:

The horizontal reaction force is 230.3 N.

Explanation:

Given that,

Length l= 14.0 m

Weight of ladder F = 490 N

Angle = 65°

Weight of firefighter F'= 850 N

Height l'= 4.10 m

Suppose horizontal force magnitude N direction vertical force magnitude N direction

We need to calculate the horizontal reaction force

Horizontal reaction force = normal reaction from wall

Vertical reaction force = weight of ladder +weight of man

[tex]F=490+850[/tex]

[tex]F=1340\ N[/tex]

We need to calculate the moment about bottom is zero

[tex]N\times l\sin\theta=F\times\dfrac{l}{2}\cos\theta+F'\times l'\cos\theta[/tex]

Put the value in the equation

[tex]N\times14\sin(65)=490\times7\cos(65)+850\times4.10\cos(65)[/tex]

[tex]N=\dfrac{490\times7\cot(65)+850\times4.10\cot(65)}{14}[/tex]

[tex]N=230.3\ N[/tex]

Hence, The horizontal reaction force is 230.3 N.