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

Click For Summary
The discussion focuses on the correct representation of free body diagrams (FBD) for two blocks connected by a string and moving up a ramp. There is an emphasis on properly angling gravity in the FBD for the 30kg block, as it was initially depicted moving horizontally. Participants suggest correcting the equations for the 30kg block to account for the ramp's slope and recommend using variables instead of specific numbers for mass and forces at this stage. Once the equations are correctly established, the next step involves eliminating unknowns to solve for tension in the strings. Accurate diagramming and equation formulation are crucial for understanding the forces at play in this scenario.
TjGrinnell
Messages
11
Reaction score
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.
Page 1.jpg
Page 2.jpg
 
Physics news on Phys.org
Looks good so far, except that your FBD for the 30kg block has it moving horizontally. Both blocks are going up the ramp.
 
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.
 
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.
 

Thread 'Magnitude of buoyant force in fluids of different densities'

The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?
View full post »

Similar threads

Force pulling on a string at an angle with a block at the other end
  • · Replies 2 ·
Replies
2
Views
1K
Tension in a string connecting two blocks having equal and opposite velocities
  • · Replies 21 ·
Replies
21
Views
830
Analyzing acceleration of block on a ramp connected to a pulley
  • · Replies 15 ·
Replies
15
Views
2K
Block tied to a fixed string on an accelerating wedge
  • · Replies 37 ·
2
Replies
37
Views
2K
Finding the work done by a block
  • · Replies 4 ·
Replies
4
Views
3K
Pulling down on the string connected to a whirling block on a table
  • · Replies 1 ·
Replies
1
Views
2K
Help again in interpreting a pulley with a spring and a block
  • · Replies 52 ·
2
Replies
52
Views
3K
Find tension in string between two blocks on horizontal surface
  • · Replies 4 ·
Replies
4
Views
1K
Trajectory of a mass element in a string overhanging a pulley
  • · Replies 19 ·
Replies
19
Views
2K
Calculate speed of block at the end of the ramp
  • · Replies 10 ·
Replies
10
Views
5K