Bathroom scale being compressed but jumping on it


by kavipach
Tags: bathroom, compressed, jumping, scale
kavipach
kavipach is offline
#1
Jul17-09, 12:49 AM
P: 20
1. The problem statement, all variables and given/known data
If you stand on a bathroom scale, the spring inside the scale compresses 0.55mm, and it tells you your weight is 760N.
Now if you jump on the scale from a height of 1.3 m, what does the scale read at its peak?
Phys.Org News Partner Science news on Phys.org
Review: With Galaxy S5, Samsung proves less can be more
Making graphene in your kitchen
Study casts doubt on climate benefit of biofuels from corn residue
rock.freak667
rock.freak667 is offline
#2
Jul17-09, 12:55 AM
HW Helper
P: 6,213
What are your thoughts on the question? Post your attempt.
kavipach
kavipach is offline
#3
Jul17-09, 01:04 AM
P: 20
well i tried a few things... i found the persons mass which is 77.55kg.Since F=ma,and we have m, i tired using kinamatics to find a but finding the velocity of the person just before impact. Then i got stuck. I dont know how to go about this question.

rock.freak667
rock.freak667 is offline
#4
Jul17-09, 01:09 AM
HW Helper
P: 6,213

Bathroom scale being compressed but jumping on it


Quote Quote by kavipach View Post
well i tried a few things... i found the persons mass which is 77.55kg.Since F=ma,and we have m, i tired using kinamatics to find a but finding the velocity of the person just before impact. Then i got stuck. I dont know how to go about this question.
So when the person stands on the scale, they weigh 760N. This means that the spring compresses. Do you know a formula that relates force and extension?
kavipach
kavipach is offline
#5
Jul17-09, 01:11 AM
P: 20
ya hookes law...F=kx.
kavipach
kavipach is offline
#6
Jul17-09, 01:11 AM
P: 20
where k equals spring constant and x equals displacment
rock.freak667
rock.freak667 is offline
#7
Jul17-09, 01:14 AM
HW Helper
P: 6,213
Quote Quote by kavipach View Post
ya hookes law...F=kx.
yes

Quote Quote by kavipach View Post
where k equals spring constant and x equals displacment
good.


So can you find the spring constant,k using the information in the first line of the question?
kavipach
kavipach is offline
#8
Jul17-09, 01:18 AM
P: 20
according to this the constant equals to 1381818.2 is this right
rock.freak667
rock.freak667 is offline
#9
Jul17-09, 01:22 AM
HW Helper
P: 6,213
Quote Quote by kavipach View Post
according to this the constant equals to 1381818.2 is this right
1381818.2 N/m yes, remember to put in your units.


So second line now. If the person is at 1.3m in the air, what type of energy does he have? This energy is converted into the energy needed to compress the spring a displacement,x, at the peak.
kavipach
kavipach is offline
#10
Jul17-09, 01:24 AM
P: 20
potential energy?
rock.freak667
rock.freak667 is offline
#11
Jul17-09, 01:26 AM
HW Helper
P: 6,213
Quote Quote by kavipach View Post
potential energy?
yes. What is the formula for gravitational potential energy? And what is the formula for the energy stored by a spring?
kavipach
kavipach is offline
#12
Jul17-09, 01:33 AM
P: 20
The formula for gravitational potential energy is U=mgy where u equals the p.e, m equals mass and y is the displacement. the formula for the energy storedd in a spring is U=1/2kx^2
rock.freak667
rock.freak667 is offline
#13
Jul17-09, 01:36 AM
HW Helper
P: 6,213
Quote Quote by kavipach View Post
The formula for gravitational potential energy is U=mgy where u equals the p.e, m equals mass and y is the displacement. the formula for the energy storedd in a spring is U=1/2kx^2
So if all the gravitational energy is converted to energy stored in the spring, that makes

gravitational p.e. = energy stored in the spring.


Can you find the compression,x for the scale now?
kavipach
kavipach is offline
#14
Jul17-09, 01:38 AM
P: 20
ya i think i can..thanks for all the help..your a life saver


Register to reply

Related Discussions
Spring Scale, the force will the scale read? Introductory Physics Homework 2
Paint my bathroom General Discussion 16
bathroom scale Introductory Physics Homework 7