• Support PF! Buy your school textbooks, materials and every day products Here!

Basic forces problem: which has a higher acceleration?

  • Thread starter JSmithDawg
  • Start date
  • #1

Homework Statement


In which situation does block m experience a larger acceleration? In case 1, the 10kg mass is hanging from a rope and falling. In case 2, a hand is providing a constant downward force. Assume the rope is massless.
upload_2014-12-17_16-3-36.png


Homework Equations


F=ma

The Attempt at a Solution


The force applied to m in case 1 is 98N. Gravity is acting on both 'm' and 10kg, but since 'm' is on top of a table (which provides a normal force), it's going to have no effect on the system's acceleration. Knowing F=ma, F=10kg(9.8 m/s^2), F=98N. Thus, the force in case 1 is equal to the force in case 2. However, the online quiz I did told me that case 2 has the higher acceleration. How is this possible if the downward force is the same in both situations?
 

Answers and Replies

  • #2
gneill
Mentor
20,792
2,770
What's the total mass being accelerated in each case?
 
  • #3
PeroK
Science Advisor
Homework Helper
Insights Author
Gold Member
12,327
5,121
You could try drawing "the hand of gravity" in case 1.
 
  • #4
The total mass being accelerated for case one is 10kg+m, and for case two it's m. But isn't the 'm' insignificant when looking at how much force is applied to each system? Wait, but it might be significant when determining acceleration. F=ma, so 98N=11kg(a) vs. 98N = 1kg(a). That makes sense that case two will accelerate faster! Thank you for hinting at the law of inertia!
 

Related Threads on Basic forces problem: which has a higher acceleration?

  • Last Post
Replies
3
Views
2K
Replies
12
Views
1K
Replies
4
Views
1K
  • Last Post
Replies
2
Views
916
  • Last Post
Replies
4
Views
492
Replies
3
Views
2K
Replies
1
Views
953
  • Last Post
Replies
8
Views
1K
Replies
4
Views
2K
  • Last Post
Replies
5
Views
13K
Top