Respuesta :
Answer: We will use the Newton's law of motion and the friction law to analyze the situation.
Step-by-step explanation: The force that the road exerts on the tyres is [tex]F=1500[/tex] N vertically upwards. Since the tires are sliding we may use the expression for kinetic friction [tex]F_{fr}=kF[/tex] where [tex]k[/tex] is the coefficient of kinetic friction. This force is acting in the direction opposite of motion. From the Newton's second law we have that
[tex]ma=F_{fr}=kF[/tex]
yielding
[tex]a=\frac{kF}{m}[/tex]
where $a$ is the deceleration of the truck. Now if the initial speed is [tex]v_0[/tex] and the speed after the braking is [tex]v[/tex] we have the formula
[tex]v^2=v_0^2-2ad,[/tex]
where [tex]d=25[/tex] m is the skidding distance. If we are asked that the truck stops, this means that [tex]v=0[/tex] so the previous formula yields
[tex]v_0^2=2ad[/tex]
further yielding
[tex]v_0^2=2\frac{kF}{m}d.[/tex]
From this formula we can calculate all the other quantities that may be required.
Answer: -50,000 J
Step-by-step explanation:
The change in kinetic energy of the bus is equal to the net work done on the bus.
Delta K = Wnet = Fnet d cos angle
We can find the net work from the net force parallel to the direction of travel and the distance travelled.
Since the force is directed opposite the displacement of the bus to bring it to a stop, the angle between the force and displacement vectors is angle = 180 degrees
ΔK =
=Fdcosθ
=(2000N)(25m)(cos180°)
=−50000J
The bus loses 50000 joules of kinetic energy.
The answer is -50000J.
