Ex: formula puteri, formule analiza financiara, inmultirea radicalilor exercitii rezolvate
Custom Search

A child pulls a sled with a mass of m = 4 kg, with a force F which makes an angle ά in the direction of movement and prints an acceleration of 3 m / s2. If the friction force between the sled and snow is Ff = 5N, what is the mechanical work value performed by the child to the sled on the distance of 4 m?

A child pulls a sled with a mass of m = 4 kg, with a force F which makes an angle ά in the direction of movement and prints an acceleration of 3 m / s2.
If the friction force between the sled and snow is Ff = 5N, what is the mechanical work value performed by the child to the sled on the distance of 4 m?

Solution:

The force that produces mechanical work is:

Force : Fx = Fcos ά 


we calculate the force that produce mechanical work by applying the fundamental relation of dynamics when the sled moves:








Ff  + N + F + mg = ma       (relation 1)

Using relation 1 on the direction of Ox axis we obtain:

-Ff + Fcos ά = ma
=> Fcos ά = ma +Ff

The mechanical work produced by the force F is given by relation:

L = (Ff + ma)*d
=> (5N + 4 Kg + 3m/s2) * 4

Niciun comentariu: