Crate pulled up incline, kinetic energy and speed; picture included

In summary: Remember that work (energy) is measured in Joules (J) and force is measured in Newtons (N).In summary, the problem involves a crate being pulled up a rough incline by a 150 N force over a distance of 5.94 m. The acceleration of gravity is given as 9.8 m/s^2. The questions ask for the change in kinetic energy of the crate, and its speed after being pulled the 5.94 m. The equations W = delta K and delta K = 1/2 mvf^2 are used to solve the problem, taking into account the work done by conservative and non-conservative forces.
  • #1
gap0063
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Homework Statement


A crate is pulled by a force (parallel to the incline) up a rough incline. The crate has an initial speed shown in the figure below. The crate is pulled a distance of 5.94 m on the incline by a 150 N force.
The acceleration of gravity is 9.8 m/s2 .
[PLAIN]http://img801.imageshack.us/img801/849/problem1011.jpg
a) What is the change in kinetic energy of the crate?
Answer in units of J.
b) What is the speed of the crate after it is pulled the 5.94 m?
Answer in units of m/s.

Homework Equations


(1)W= delta K= Integral Fx dx= Integral Sum of F dr= Integral Sum of F dr + Integral fk dr= Sum of W - fkd
(2)Delta K= 1/2 mvf^2

The Attempt at a Solution


Wells for part a) I tried equation (1)and got 150 N- (0.399* 5.94)=147.63 J... which I don't know if its right
and for b) (if part a is right) I used equation (2) vf=sq rt ( (2/m)*147.63)= 4.76574 m/s
 
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  • #2
When using W =delta K , W includes the work done by gravity or any other conservative forces, when present. It is best to use conservation of total energy, Work done by non - conservative forces (like friction and the applied force) equals delta __??__ + delta __??_.

The problem asks for the change in Kinetic Energy, in addition to its speed.

You are getting your energy and force units mixed up.
 

Related to Crate pulled up incline, kinetic energy and speed; picture included

1. What is the relationship between the incline of a ramp and the kinetic energy of a crate pulled up the ramp?

The incline of a ramp affects the amount of kinetic energy a crate has while being pulled up. As the incline increases, the kinetic energy also increases. This is because the higher the incline, the more work is done to lift the crate against gravity, resulting in an increase in kinetic energy.

2. How does the weight of the crate affect its speed while being pulled up an incline?

The weight of the crate does not directly affect its speed while being pulled up an incline. The speed is determined by the amount of force applied to the crate and the incline of the ramp. However, a heavier crate may require more force to be pulled up the incline, resulting in a slower speed.

3. Can the kinetic energy of the crate be greater than its potential energy while being pulled up an incline?

No, the kinetic energy of the crate cannot be greater than its potential energy while being pulled up an incline. The potential energy is at its maximum when the crate is at the top of the incline, and as it moves down the incline, the potential energy is converted into kinetic energy. Thus, the kinetic energy can only be equal to or less than the potential energy.

4. How does friction affect the speed of the crate being pulled up an incline?

Friction can significantly affect the speed of the crate being pulled up an incline. Friction acts in the opposite direction of motion and can decrease the speed of the crate. It also causes the crate to lose some of its kinetic energy, which can result in a slower speed.

5. Is the kinetic energy of the crate constant while being pulled up an incline?

No, the kinetic energy of the crate is not constant while being pulled up an incline. The kinetic energy increases as the crate moves up the incline, reaches its maximum at the top, and then decreases as it moves down the incline. This is because the work done by the force pulling the crate is constantly changing as the height and speed of the crate change.

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