Two blocks connected with a small string pulled up a ramp by string

In summary, the conversation discusses a problem with a diagram for two blocks moving up a ramp, with one block having a horizontal movement instead of an angled gravity. The person is unsure of which formula to use to calculate the tension forces for each string and is asking for a hint. They are advised to correct the equations for the 30kg block to account for the slope and to use variables for the masses and forces instead of plugging in numbers.
  • #1
TjGrinnell
11
1
Homework Statement
I have two blocks, one with a mass of 20.0 kg and one with a mass of 30.0 kg. I need to move them up a ramp that is inclined at (14)° above horizontal. I put them onto the bottom of the ramp and tie the two block together with a short piece of string that runs parallel to the ramp. I tie a longer piece of string to the 20.0-kg block and use it to pull both blocks up the ramp. The longer string is inclined at 40.0° from horizontal. I pull the longer string, and the blocks move up the ramp with an acceleration of 1.00 m/s^2. Assume the coefficient of kinetic friction between each block and the ramp is 0.150.

Determine the magnitudes of the net force on the 30.0-kg block, the friction force on the 30.0-kg block, and the tension in the short string.

Determine the magnitudes of the net force on the 20.0-kg block, the friction force on the 20.0-kg block, and the tension in the longer string.

I pull on the string while the blocks move 2.40 m. What is the speed of the 30-kg block at the end of that time?
Relevant Equations
Very confused on what to do with the two strings and how to calculate the magnitude of Net forces because of this.
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  • #2
Looks good so far, except that your FBD for the 30kg block has it moving horizontally. Both blocks are going up the ramp.
 
  • #3
haruspex said:
Looks good so far, except that your FBD for the 30kg block has it moving horizontally. Both blocks are going up the ramp.
I did forget to angle gravity as I did in the 20kg diagram, but even after fixing this I am not sure what formula to use in order to calculate the forces of the tension for either string.
If you could even just give a hint that would be very helpful.
 
  • #4
TjGrinnell said:
I did forget to angle gravity as I did in the 20kg diagram, but even after fixing this I am not sure what formula to use in order to calculate the forces of the tension for either string.
If you could even just give a hint that would be very helpful.
Your equations for the 20kg block were fine. Correct your 30kg equations to take account of the slope and post them.
Avoid plugging in any numbers for the masses and forces at this stage. Just create variables for the two masses.

When you have all the equations you can proceed to eliminating unknowns and solve them.
 

1. How does the angle of the ramp affect the movement of the blocks?

The angle of the ramp affects the movement of the blocks by changing the force required to pull them up. As the angle increases, the force needed to overcome gravity also increases, making it more difficult to pull the blocks up the ramp.

2. What is the role of the string in this experiment?

The string serves as a connection between the two blocks, allowing them to move together and transfer force between each other. It also acts as the pulling force that moves the blocks up the ramp.

3. How does the mass of the blocks affect their movement?

The mass of the blocks affects their movement by increasing the force of gravity acting on them. This makes it more difficult to pull them up the ramp, requiring more force from the string.

4. What is the relationship between the force applied by the string and the force of gravity?

The force applied by the string must be greater than the force of gravity in order to move the blocks up the ramp. This is because the string must not only overcome the force of gravity, but also provide enough force to move the blocks against the resistance of the ramp.

5. How does friction play a role in this experiment?

Friction between the blocks and the ramp can make it more difficult to move the blocks up the ramp. This is because friction acts in the opposite direction of the movement, creating resistance that must be overcome by the force of the string pulling the blocks.

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