Work-energy theorem , not sure what I am doing wrong.

In summary, the work-energy theorem is used to find the length of a rough patch on a frictionless ice rink that reduces a skater's speed by 42% due to a friction force of 20% of her weight. The calculations using this theorem result in a length of 3.85 meters for the rough patch. However, there may be a mistake in the calculation and the value for the reduced speed should be 0.58m/s, not 0.42m/s. The work-energy theorem states that the change in kinetic energy is equal to the work done by all forces acting on an object. The equation used is -0.2gs = (1/2)mvf^2 - (1
  • #1
1man
17
0
On an essentially frictionless, horizontal ice rink, a skater moving at 6.0 m/s encounters a rough patch that reduces her speed by 42 \% due to a friction force that is 20 \% of her weight.

Use the work-energy theorem to find the length of this rough patch.

i do: [.42 * (.5) * (6)^2]/ [.2 * 9.8]=3.85
but i get the wrong answer can anyone help, does the answer need to be negative, what am i doing wrong.
 
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  • #2
What does the work-energy theorem state?

What is the change of the KE if the speed is reduced to 42% of the original 6 m/s ?

ehild
 
  • #3
K_2-K_1 where k=1/2*m*v^2, thank you, it would be .58v not .42, in the equation
-.2gs = (1/2)mvf^2 - (1/2)mvi^2 where the m cancel
 

Related to Work-energy theorem , not sure what I am doing wrong.

What is the work-energy theorem?

The work-energy theorem is a fundamental principle in physics that states that the net work done on an object is equal to the change in its kinetic energy. In other words, when a force is applied to an object, it either speeds up or slows down, and the work done by that force is equal to the change in the object's kinetic energy.

How is the work-energy theorem derived?

The work-energy theorem is derived from Newton's second law of motion, which states that the net force acting on an object is equal to the mass of the object times its acceleration. By using this equation and integrating it with respect to displacement, we can arrive at the work-energy theorem.

What is the relationship between work and energy according to the work-energy theorem?

The work-energy theorem states that work and energy are directly related, with work being the transfer of energy from one form to another. Work can change the kinetic energy of an object, and the work done on an object is equal to the change in its kinetic energy.

What are the units of measurement for work and energy?

The units of measurement for work and energy are both joules (J) in the International System of Units (SI). However, in some cases, other units such as foot-pounds (ft-lb) or calories (cal) may be used.

How is the work-energy theorem applied in real-world situations?

The work-energy theorem has numerous applications in real-world situations, such as calculating the energy required to lift an object, the force needed to move an object a certain distance, or the work done by a machine. It is also used in fields such as engineering and mechanics to analyze and design systems.

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