How many rocks/min to mantain a constant speed

Click For Summary
SUMMARY

The discussion focuses on calculating the number of rocks a child must throw from a wagon to maintain a constant speed against a frictional force of 2.0 N. The child throws rocks weighing 0.60 kg at a speed of 10 m/s. The derived thrust is calculated as 0.1 N, leading to a mass flow rate of 0.2 kg/s, which translates to 12 rocks per minute. The calculations confirm that to counteract the frictional force, the child must throw rocks at this rate to sustain motion.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Basic knowledge of thrust and its calculation
  • Familiarity with mass flow rate concepts
  • Ability to perform unit conversions (kg/s to rocks/min)
NEXT STEPS
  • Study Newton's second law of motion in detail
  • Learn about thrust calculations in mechanics
  • Explore the concept of mass flow rate and its applications
  • Practice problems involving frictional forces and motion
USEFUL FOR

Students in physics, educators teaching mechanics, and anyone interested in practical applications of Newton's laws in real-world scenarios.

tironci
Messages
1
Reaction score
0
This is the problem i am trying to solve:

A child sits in a wagon with a pile of 0.60-kg rocks. If she can throw each rock with a speed of 10 m/s relative to the ground, causing the wagon to move, how many rocks must she throw per minute to maintain a constant average speed against a 2.0-N force of friction? I need to find change in m/ change in t for rocks/min

m/t = thrust/v , now i found thrust = (m/t)v -> (0.6kg/60s) 10m/s = 0.1 N

m/t = thrust/ v -> 0.1/10 = 0.01 kg/s if i turn this it kg/min 0.01/60 = 1.7x10^-4

but this doesn't seem to be the right correct answer?

Any help would be appreciated
 
Physics news on Phys.org
F = v(dm/dt)

2 = 10(dm/dt)
dm/dt = 0.2 (thats per second)
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 42 ·
2
Replies
42
Views
6K
Replies
1
Views
4K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 39 ·
2
Replies
39
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K