# Problem involving a skier, friction and conservation of energy

• honeyspells
In summary: B)Now moving horizontally, the skier crosses a patch of soft snow, where the coefficient of friction is μk = 0.210. If the patch is of width 64.0m and the average force of air resistance on the skier is 180N , how fast is she going after crossing the patch?μk = 0.210v= μkv= (0.210)(64.0m)(180N)= 6.452m/sC)After crossing the patch of soft snow, the skier hits a snowdrift and penetrates a distance 2.90m into it before coming to a stop. What is the average force exerted on her by
honeyspells
::A skier of mass 63.0kg starts from rest at the top of a ski slope of height 62.0m .A skier of mass 63.0kg starts from rest at the top of a ski slope of height 62.0m .A) If frictional forces do −1.00×104J of work on her as she descends, how fast is she going at the bottom of the slope?
Take free fall acceleration to be g = 9.80m/s2 .

B) Now moving horizontally, the skier crosses a patch of soft snow, where the coefficient of friction is μk = 0.210. If the patch is of width 64.0m and the average force of air resistance on the skier is 180N , how fast is she going after crossing the patch?

C) After crossing the patch of soft snow, the skier hits a snowdrift and penetrates a distance 2.90m into it before coming to a stop. What is the average force exerted on her by the snowdrift as it stops her?

m=63.0kg
g= 9.8m/s2
H=62.0m

What I've done:
A)
U= mgH= (63.0kg)(9.8m/s2)(62.0m)= 38278.8 N-m

NET FORCE= 38278.8-1000= 37278.8

37278.8= (1/2)mv2
37278.8= (31.5)v2
so v= 34.401

Mastering physics says that is WRONG. I've checked my math over and over again. Where did I go wrong?

tips?

Last edited:
Sorry but this is completely wrong, the formula you are using for potential energy gives you energy for an answer, not a force. The equation you want to use is the law of conservation of energy:
$\frac{1}{2}m{v_1}^2 + mgy_1 = \frac{1}{2}m{v_2}^2 + mgy_2 + F_{fr}l$

honeyspells said:
A) If frictional forces do −1.00×104J of work on her as she descends, how fast is she going at the bottom of the slope?

honeyspells said:
U= mgH= (63.0kg)(9.8m/s2)(62.0m)= 38278.8 N-m

NET FORCE= 38278.8-1000= 37278.8

You're calculating energy, not force. Note that from the question statement that the work done by friction has a magnitude of 1 x 104. That's 10,000 not 1000 Joules.

## 1. How does friction affect a skier's movement?

Friction is a force that opposes motion, so it can slow down a skier's movement. When a skier is moving downhill, friction from the snow and air can act against their motion and cause them to slow down. However, some friction is necessary for a skier to keep their balance and control their speed.

## 2. What role does conservation of energy play in skiing?

Conservation of energy states that energy cannot be created or destroyed, only transferred or converted. In skiing, this means that the initial potential energy the skier has at the top of the slope is converted into kinetic energy as they move downhill. Friction and air resistance will then convert some of this kinetic energy into other forms, such as heat and sound.

## 3. How does the skier's body position affect their energy conservation?

The skier's body position can greatly impact their energy conservation. By keeping their body low and close to the ground, they can reduce air resistance and maintain their speed for longer. Additionally, leaning forward can help them transfer their potential energy into kinetic energy more efficiently, while leaning back can cause them to lose energy and slow down.

## 4. Why is it important for skiers to wax their skis?

Waxing a ski involves adding a layer of wax to the base of the ski, which reduces the friction between the ski and the snow. This allows the skier to maintain their speed for longer and use less energy while skiing. It also helps with control and maneuverability on the slopes.

## 5. How does the slope of the hill affect the skier's energy conservation?

The slope of the hill directly affects the skier's energy conservation. A steeper slope will have more gravitational potential energy, which will convert into more kinetic energy as the skier moves downhill. This can result in a faster and more intense ride. On the other hand, a gentler slope will have less potential energy and the skier will need to work harder to maintain their speed.

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