Physics Homework Help: Calculating Frictional Force and Tension on a Slope

[Tibaloca]

frictional force! help!

Hi There,
I'm having trouble with these physics question in my homework:

1. An object of mass 1.5kg rests on a slope making an angle of 30 degrees, with the horizantal calculate:

a) the frictional force and
b) the normal reaction acting on the object. Gravitational field strengh = 9.8N/kg

2. Two tug boats pull a ship so that it moves with a constant velocity. Each of the tugs produces a tension T at an angle of 28 degrees to the direction the ship is moving. The drag on the ship is 220kN. Calculate T.

I would be really grateful if you go could help me with this, its driving me nuts...oh and by the way with question 1, I worked out the normal force, which I think is what I had to do and got 1.3N (1dp)...after that I got stuck..especially with the whole coefficent friction :yuck:

 

[Rake-MC]

Okay we'll start with question 1.
What do we know about the normal reaction force?
Well, it's a normal force, which means that it acts at a right angle to the plane it's resting on (the force pushing on the mass).

You know that gravity acts straight down. So you just need to calculate the component of weight (mg) that is perpendicular to the plane.

That sums up b)

For a):

The question states that the object is at rest. This implies that the net force must be zero (and so is initial velocity). Static friction (and kinetic friction) is measured by multiplying a coeffiecient of the friction by the normal reaction force.
Sum up all of the forces acting on the box and let them equal zero (sum up each dimension individually), the only variable you do not have is friction.

 

[baba89]

Hi there,

I understand your frustration with these questions. Calculating frictional force and tension on a slope can be tricky, but it's important to understand these concepts in order to apply them to real-world situations. Let's break down each question and go through the steps to solve them.

1. For the first question, we have an object of mass 1.5kg resting on a slope with an angle of 30 degrees. To calculate the frictional force, we need to use the formula Ff = μN, where μ is the coefficient of friction and N is the normal force. The normal force is the force exerted by the surface on the object perpendicular to the surface. In this case, since the object is on a slope, the normal force will be equal to the component of the object's weight that is perpendicular to the slope. This can be calculated using the formula N = mgcosθ, where m is the mass of the object, g is the gravitational field strength, and θ is the angle of the slope. Plugging in the values, we get N = (1.5kg)(9.8N/kg)cos30° = 12.75N. Now, we need to find the coefficient of friction. This value depends on the surfaces in contact, but for this problem, let's assume it is 0.2. Plugging in all the values, we get Ff = (0.2)(12.75N) = 2.55N. This is the frictional force acting on the object.

To calculate the normal reaction, we can use the formula N = mgcosθ, as we did before. In this case, the normal reaction will be equal to the component of the object's weight that is parallel to the slope. Plugging in the values, we get N = (1.5kg)(9.8N/kg)sin30° = 4.9N. This is the normal reaction acting on the object.

2. For the second question, we have two tug boats pulling a ship at a constant velocity. The tension produced by each tug is at an angle of 28 degrees to the direction of motion. We need to find the total tension produced by both tugs in order to overcome the drag force of 220kN and keep the ship moving at a constant velocity. To do this, we can use the formula T = Fcosθ, where T