Change in kinetic energy Velocity not given

In summary, the problem involves two forces, F1 = 70.0 N and F2 = 35.0N, acting in opposite directions on a block on a frictionless surface. The block starts at position xi = -2.00cm and ends at position Xf = 4.00cm. The net force on the block and the equations for determining the final velocity and time are needed to find the change in kinetic energy. The equation for kinetic energy is 1/2 mv^2 and the work done on the block is equal to the change in kinetic energy.
  • #1
rock_star
13
0
change in kinetic energy! Velocity not given :(

Homework Statement


Two forces, of magnitudes F1 = 70.0 N and F2 = 35.0N , act in opposite directions on a block, which sits atop a frictionless surface, as shown in the figure. Initially, the center of the block is at position xi = -2.00cm . At some later time, the block has moved to the right, and its center is at a new position, Xf = 4.00 cm .

Determine the change in the kinetic energy of the block as it moves from Xi= -2.00 to X f= 4.00

Link to the diagram : http://session.masteringphysics.com/problemAsset/1011314/13/MWE_wi_5.jpg

Homework Equations


Kinetic energy = 1/2 mv^2


The Attempt at a Solution



Since it is starting from rest, initial velocity, V0 = 0 and then d = Vf t

But here Vf is not given..
I am not sure how to proceed when there is no velocity given

Can any more help me ?

Thanks a lot before hand
 
Last edited:
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  • #2


rock_star said:

Homework Statement


Two forces, of magnitudes F1 = 70.0 N and F2 = 35.0N , act in opposite directions on a block, which sits atop a frictionless surface, as shown in the figure. Initially, the center of the block is at position xi = -2.00cm . At some later time, the block has moved to the right, and its center is at a new position, Xf = 4.00 cm .

Determine the change in the kinetic energy of the block as it moves from Xi= -2.00 to X f= 4.00

Link to the diagram : http://session.masteringphysics.com/problemAsset/1011314/13/MWE_wi_5.jpg

Homework Equations


Kinetic energy = 1/2 mv^2


The Attempt at a Solution



Since it is starting from rest, initial velocity, V0 = 0 and then d = Vf t

But here Vf is not given..
I am not sure how to proceed when there is no velocity given

Can any more help me ?

Thanks a lot before hand

What is the net force acting on the block? Just keep the mass and velocity as variables, m and V for now. Write the equations to tell you how long it takes to get to the 2nd position, and what the final velocity is. Then see if some of the variable terms cancel out...
 
  • #3


Change in kinetic energy = work done on the block = Force X displacement.
In the problem force and displacement is given. That is sufficient to find the KE.
 
  • #4


Thank a lot everyone! :)
I understood it! :D
Thank a ton everyone!
 

1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is dependent on the mass and velocity of the object.

2. How is kinetic energy calculated?

Kinetic energy is calculated using the formula KE = 1/2 * m * v^2, where m is the mass of the object and v is the velocity of the object.

3. Can kinetic energy change without a change in velocity?

Yes, kinetic energy can change without a change in velocity. This can happen if the mass of the object changes, as kinetic energy is directly proportional to mass.

4. What factors affect the change in kinetic energy?

The change in kinetic energy is affected by the mass and velocity of the object. Other factors such as air resistance and friction can also affect the change in kinetic energy.

5. How does an increase in mass affect the change in kinetic energy?

An increase in mass will result in an increase in kinetic energy, as long as the velocity remains constant. This is because kinetic energy is directly proportional to mass.

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