How long does it take a car to cross a 20m bridge if it starts from rest and accelerates at 5 m/s^2?
1 answer:
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The diagram of the object on the inclined plane is shown below
The mass of 7kg is exerted on the plane surface. It is acted upon by gravity. The force exerted on the surface is calculated by applying the formula,
F = mass x acceleration due to gravity
Assumme acceleration due to gravity is 9.8m/s^2, then
Force = 7 x 9.8 = 68.6N
The surface exerts an opposite force of the same magnitude with the force of the object but in opposite direction. Since it is inclined at an angle of 36.9 degrees,
Normal force = mgCosθ = 68.6Cos36.9 = 54.86N
Recall, frictional force = normal reaction x coefficient of friction
Given that coefficient of kinetic friction = 0.35,
Frictional force = 54.86 x 0.35 = 19.201N
This is the force that must be overcome to keep the object moving.
The force pulling the object upwards along the inclined plane is
mgSinθ = 7 x 9.8 x Sin36.9 = 41.19N
Since the velocity is constant, it means that there is no acceleration. The net force is zero. The force required to pull the mass and make it move at constant velocity must be equal to the sum of the exerted force and the the frictional force(Since it involves coeffricient of kinetic friction, it would cause the object to keep moving)
Thus,
Required force = 19.2 + 41.19 = 60.4N
Option E is correct
