# A grade 12 physics dynamics problem

• Scatteredheroes
In summary, a boy is pulling an 80 N sled up a 15 degree hill with a 35 N force at an angle of 35 degrees to the horizontal. The coefficient of kinetic friction between the snow and sled is unknown. When the boy jumps on the sled (weighing 50 kg), he accelerates down the hill. The relevant equations are Fnet=ma and Ffk = μfn. The main problem is finding the required forces using the angles in the diagram. To solve this, symbols can be assigned to all values and the algebra can be done symbolically before plugging in the numerical values at the end.
Scatteredheroes

## Homework Statement

A boy drags his 80 n sled at a constant speed up a 15 degree hill. He does so by pulling with a 35 n force on a rope attached to a sled. If the rope is inclined at 35 degrees to the horizontal, what is the coefficient of kinetic friction between snow and sled

At the top of hill, he jumps on sled (weighing 50 kg, the boy) and slides down the hill. What is his acceleration?

## Homework Equations

Fnet= ma

Ffk = mew fn

And so on, so forth.

## The Attempt at a Solution

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I drew a FBd, including angles, and force locations, but I do not know how to use the angles to find the required forces. As well, as a general question, how do you use angles in the diagram to find things?

My main problem is that I know the Fg, which is ma (9.8)

After that, I get slightly lost due to the angles, and am unable to find even the most basic fn.

Scatteredheroes said:
I drew a FBd, including angles, and force locations, but I do not know how to use the angles to find the required forces.
if you can't post the diagram, at least try to describe it. What forces operate, what magnitudes and what directions?
Invent symbols for all values so that the algebra can be done symbolically. Only plug the numbers back in at the end.

## 1. What is Newton's first law of motion?

Newton's first law of motion states that an object will remain at rest or in a state of uniform motion unless acted upon by an external force.

## 2. How do you calculate the net force on an object?

The net force on an object is calculated by adding together all the individual forces acting on the object, taking into account their direction and magnitude.

## 3. What is the difference between mass and weight?

Mass is a measure of the amount of matter in an object, while weight is the force of gravity acting on an object. Mass is measured in kilograms (kg) and weight is measured in newtons (N).

## 4. How does friction affect the motion of an object?

Friction is a force that opposes the motion of an object and can cause it to slow down or stop. The amount of friction depends on the type of surface and the force pushing the objects together.

## 5. Can an object have a constant velocity and still have a net force acting on it?

Yes, an object can have a constant velocity and a net force acting on it if the forces are balanced. This means that the object is moving at a constant speed in a straight line, with no change in direction.

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