Newton's Second Law - Net Force and Constant Acceleration

AI Thread Summary
A discussion on Newton's Second Law focused on calculating the net force exerted on a 92 kg water skier accelerated from rest to 12 m/s over 25 meters. Participants emphasized the need to determine acceleration and time to apply the formula F = ma correctly. The calculation of time to cover the distance with constant acceleration was debated, with one participant arriving at approximately 2.08 seconds. Clarifications were sought regarding the correct interpretation of speed and the components of net force. The conversation highlighted the importance of using appropriate equations to link distance, time, and acceleration for accurate force calculations.
electronXguy419
Messages
3
Reaction score
0
1. A 92 kg water skier floating in a lake is pulled from rest to a speed of 12 meters/second in a distance of 25 meters. What is the net force exerted on the skier, with the assumption that his acceleration is constant?2. Force = Mass x Acceleration3. As far as I know, from using the equation from #2, I did 92kg x 12m/s, and got 1.104k Newtons.
 
Physics news on Phys.org
Hello guy, welcome to PF :smile:

As far as I know is not far enough: if you compare the dimensions you'll see that you don't get Newtons (kgm/s2) this way, but kgm/s -- which is the dimension of momentum.

So you'll need some more equations to find something with the dimension of time to get this in order. How long does it take to cover 25 m with constant acceleration and then have a speed of 12 m/s ?
 
Hi!

If I want to solve a problem in Dynamics, the first thing I do is to write down Newton's Second Law. You stated it right: F = ma
The two things we do not know here are the force, which is the solution of the exercise, and the acceleration which we have to express in another way, because we have two other data we didn't use up: the change of speed and the distance. Try to think about the definition of the acceleration (change of velocity over unit of time). We need an equation that links the distance and the time in function of the acceleration.
 
BvU said:
How long does it take to cover 25 m with constant acceleration and then have a speed of 12 m/s ?

I got approximately 2.08 seconds.
 
2.08333 s is a result. What is the calculation that gave you that result ? Because I get something else...

Suppose you have found this t. Then how do you calculate the net force exerted on the poor skier ? (I mean an equation with variable names, not a numerical result)
 
BvU said:
2.08333 s is a result. What is the calculation that gave you that result ? Because I get something else...

Suppose you have found this t. Then how do you calculate the net force exerted on the poor skier ? (I mean an equation with variable names, not a numerical result)

In answer to the first question, I took the distance (25m) and divided it by the speed (12m/s); as for the second question: Fnet = F1 + F2.
 
The speed isn't 12 m/s ! It clearly says the skier is accelerated with a constant acceleration from rest to 12 m/s.
RE the equation: FNET is supposed to be the answer for the exercise, but what are F1 and F2 ?
 

Similar threads

Find the acceleration of the system (2 blocks sliding on a table)
Replies
23
Views
2K
Blowing Into Your Own Sail
Replies
25
Views
1K
Distribution of Energy when work is done on a system of 2 masses connected by a spring
Replies
17
Views
1K
Effect on net torque and net force on spools
Replies
9
Views
2K
Explanation for Newton II giving negative mass in my Physics lab results please
Replies
44
Views
3K
Unbalanced force to find altitude of airplane
Replies
4
Views
2K
Newton's second law (My turtle named Newton being accelerated)
Replies
9
Views
2K
Newton's law problem: Pushing 2 stacked blocks on a horizontal table
Replies
13
Views
3K
Spring Problem Involving Variables and Constants Only
Replies
3
Views
1K
Two forces acting on an object given in vectors - SOLVED
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top