How to find net force using mass, distance, and time?


by elkosp16
Tags: distance, force, mass, time
elkosp16
elkosp16 is offline
#1
Nov4-09, 04:45 PM
P: 3
1. The problem statement, all variables and given/known data[/B]
A 2.0 kg otter starts from rest at the top of a muddy incline 85 cm long and slides down to the bottom in 0.50 s. What net force acts on the otter along the incline?

mass = 2.0 kg
distance = 85 cm
time = .50 s
net force = ?


2. Relevant equations
Fnet=ma

I also used.
V=x/t
a=v/t


3. The attempt at a solution
v=x/t
85/.5=170

a=v/t
170/.5=340 cm/s^2
340 cm/s^2 = 3.4 m/s^2

Fnet=ma
(2.0 kg)(3.4 m/s^2)= 6.8 N

The book says the right answer is 14 N though.
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ApexOfDE
ApexOfDE is offline
#2
Nov4-09, 06:01 PM
ApexOfDE's Avatar
P: 122
I also used.
V=x/t
a=v/t
No, velocity is not constant. It changes over time. You should read your textbook again or check this link to find appropriate formula.
Deep_Blue
Deep_Blue is offline
#3
Nov4-09, 08:58 PM
P: 2
Hi elkosp16, you need to use the formula :

Δ X = Vi*T + (1/2)*a*T^2

You already know displacement (ΔX), 85 cm (remember to convert it to meters !)
Initial velocity (Vi) is 0, because it starts at rest.
Time = .50 seconds,
Plug everything in and solve for a,

once you get acceleration, use newtons second law.
∑ F=m*a
plug in mass & acceleration, the answer is net force.


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