Final answer:
To find the force required to pull the crate up the ramp at a constant velocity, we calculate the component of gravity along the ramp and set the parallel component of the pull equal to it.
Step-by-step explanation:
The question involves determining the force necessary to pull a crate up a ramp at a constant velocity, which is a classic physics problem involving concepts of Newton's laws, net force, and work-kinetic energy principles. To solve this, we must understand that if the crate is moving at constant velocity, the net force on it is zero. This is because according to Newton's first law, an object in motion at a constant velocity will remain at that velocity unless acted upon by an unbalanced force.
In this case, we need to find the component of the gravitational force acting down the ramp (parallel to it) and then apply the force required to counteract this component. The gravitational force can be calculated by multiplying the weight of the crate (150 N) by the sine of the angle of the incline (sin 15°). The force required to move the crate up the incline at a constant velocity needs to be equal and opposite to this component.
The pull makes an angle of 30° with the ramp, but we are only interested in the component of this pull parallel to the ramp's surface. Therefore, we multiply the total pull by the cosine of 30° to find the parallel component. Setting the parallel component of the pull equal to the component of the gravitational force down the ramp and solving for the magnitude of the pull gives us the answer.