How much force is required to start a block moving on level ground?

Click For Summary

Homework Help Overview

The discussion revolves around determining the force required to initiate the movement of a block on level ground, considering static and kinetic friction coefficients. The block's mass is specified as 1980 kg, and there is a follow-up question regarding the number of people needed to pull the block at a constant velocity.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the distinction between static and kinetic friction forces and their relevance to the problem. There are questions about the appropriate equations to use for both the initial force required to move the block and the subsequent calculations for moving multiple blocks over a distance.

Discussion Status

The discussion is active, with participants providing guidance on the use of static and kinetic friction in their calculations. Some participants express confusion about the application of velocity in the context of the problem, while others suggest simplifying the approach to find a solution.

Contextual Notes

Participants are working within the constraints of a homework assignment, which includes specific values for friction coefficients and the mass of the block. There is also a focus on the practical implications of moving blocks over a distance within a set timeframe.

grrer
Messages
7
Reaction score
0

Homework Statement


The Egyptian's sled system had a rather high coefficient of static friction (0.7) but a much lower coefficient of kinetic friction (0.3) How much force is required to start a block moving on level ground?
We know the block is 1980 kg

and after that:
Assume that one person is able to apply 100N the block. Using this value, how many people does it take to pull a block at constance velocity along flat ground?

Homework Equations





The Attempt at a Solution


Do i do Fs - Fk to find the answer to the first question? or is it just Fs?
 
Physics news on Phys.org
Just Fs .
 
and is the second one just fk?
 
Well why do you think static and kinetic friction are different forces? They are just names of different phases of the same force. So use Fs when block does not move and Fk when it has started moving.
 
thanks!
Assume that a comfortable walking speed for an average person is 1.33m/s Assume that the workers can only walk at half this speed while they were pulling a block, but that they would walk at this speed on the trip from the pyramid back to the quarry. At these speeds, how many blocks can one crew of 59 people, move from the quarry (5km away) to the pyramid in one ten hour work day?
 
Last edited:
I am guessing that this one is related to the last. You can use simple kinematics for this- time for one round trip, how many stones for the crew in one round trip and then for the day.You have everything just go for it.
 
what forumula do I use? I'm confused what to do with the velocity
 
Well v=distance/t, what else?
 
:S and then?
 
Last edited:
  • #10
Are you overcomplicating? Start with time for one round trip for one block. Since you have already calculated the people required for one block, you can calculate the no. of blocks a group of 59 would move in one round trip.The time for one trip divided by total working time and multiplied by no. of blocks in one trip is your answer.
 
  • #11
wow, yes i was over complicating it, thank you so much!
 
  • #12
sorry maybe i just don't understand what this question is asking but:
How long does it take a crew to accelerate a block to the walking speed?
 

Similar threads

Replies
61
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
16
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 45 ·
2
Replies
45
Views
8K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 28 ·
Replies
28
Views
4K