# Physics Problem Center Of mass HELP

• FahimP
In summary: Break the force mg into two components, one along the incline and one perpendicular to it. Resolve the forces parallel and perpendicular to the incline. Write the net force equations for Jack in the x-direction and the y-direction. Solve these equations for the x and y components of the acceleration vector.In summary, the problem involves two skiers starting from rest at different points on a hill at the same time, with different masses and slopes. The question asks to find the acceleration vector for Jack before he reaches the less steep section, and the given answer is (3.95)i + (-2.29)j. However, the answer calculated by the person asking the question does not match. To solve the problem, a free body diagram must
FahimP

## Homework Statement

The problem is asking to find the Acceleration vector before jack reaches the less steep section.
the Ans from back of book says : (3.95)i + ( -2.29 ) j

My answer does not match at all : ANY HELP PLZZZZ

anyone know how to get this ?

Two skiers, Annie and Jack, start skiing from rest at different points on a hill at the same time. Jack, with mass 85 kg, skis from the top of the hill down a steeper section with an angle of inclination of 35°. Annie, with mass 70 kg, starts from a lower point and skis a less steep section, with an angle of inclination of 20°. The length of the steeper section is 175 m.

Here is a pic :
http://s172.photobucket.com/albums/w30/afghanplayr/?action=view&current=8-p-032-alt.gif
Category

## The Attempt at a Solution

This is how i tried to find the acceleration vector :

F = mg
F = 85kg( 9.81 ) = 568.98 N

568.98sin(35) = 326.35
568.98cos(35) = 466.05

a = Fnet/m
326.35/85 = 3.83
466.05/85 = 5.48

a= ( 3.83)i + ( 5.48 ) j

I suspect that one problem is that the components into which you have resolved the gravitational acceleration vector g are components that are parallel and perpendicular to the incline. (Draw the vector decomposition and you'll see this is true). The problem is that your x and y coordinate axes are not aligned with these parallel and perpendicular directions (look at the figure).

Another problem is that Jack's weight is not the only force that acts on him (Hint: he never accelerates in the direction perpendicular to the incline, right? So something other than just gravity must be present). So, computing the net force in the x-direction and the net force in the y-direction requires a little bit more work and thought than what you've done here.

Draw a free body diagram for Jack.

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## What is the center of mass in physics?

The center of mass in physics is a point that represents the average position of all the mass in a system. It is the point where the total mass of the system can be considered to be concentrated.

## How do you calculate the center of mass?

The center of mass can be calculated by finding the weighted average of the positions of all the individual masses in a system. This is done by multiplying the mass of each object by its position and then dividing by the total mass of the system.

## Why is the center of mass important in physics?

The center of mass is important in physics because it allows us to simplify the analysis of complex systems. It helps us understand the overall motion of a system and can be used to predict how the system will behave under different conditions.

## What is the difference between center of mass and center of gravity?

The center of mass and center of gravity are often used interchangeably, but they are not exactly the same. The center of mass is a point that represents the average position of all the mass in a system, while the center of gravity is the point where the weight of an object is concentrated. In most cases, the center of mass and center of gravity are in the same location, but they can differ in systems with non-uniform gravitational fields.

## How can the center of mass be useful in solving physics problems?

The center of mass can be useful in solving physics problems by simplifying the analysis of complex systems. It allows us to treat the entire system as a single point and apply the laws of motion to this point. This can make problem-solving faster and easier in many cases.

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