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

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SUMMARY

The discussion focuses on calculating the net force acting on a 2.0 kg otter sliding down an 85 cm incline in 0.50 seconds. The correct approach involves using the equation of motion ΔX = Vi*T + (1/2)*a*T^2 to find acceleration, which is then applied in Newton's second law, Fnet = ma. The calculated net force is 14 N, as opposed to the incorrect initial calculation of 6.8 N. Key concepts include converting units and understanding variable acceleration.

PREREQUISITES
  • Understanding of Newton's second law (Fnet = ma)
  • Knowledge of kinematic equations, specifically ΔX = Vi*T + (1/2)*a*T^2
  • Ability to convert units from centimeters to meters
  • Basic grasp of acceleration and its calculation
NEXT STEPS
  • Study kinematic equations in detail, focusing on their applications in various scenarios
  • Learn about unit conversions, particularly in physics contexts
  • Explore Newton's laws of motion and their implications in real-world problems
  • Practice solving problems involving variable acceleration and net force calculations
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the principles of motion and force calculations in mechanics.

elkosp16
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Homework Statement

[/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 = ?

Homework Equations


Fnet=ma

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

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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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 http://en.wikipedia.org/wiki/Equation_of_motion" to find appropriate formula.
 
Last edited by a moderator:
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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