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:
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
=> L = 68 jouli
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