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

In summary, an otter with a mass of 2.0 kg slides down a muddy incline with a distance of 85 cm in 0.50 seconds. Using the equations of motion, the net force acting on the otter is calculated to be 6.8 N. However, this is not the correct answer as velocity is not constant and changes over time. By using the formula for displacement with initial velocity of 0, the acceleration is found to be 3.4 m/s^2 and therefore the net force is 14 N according to Newton's second law.
  • #1
elkosp16
3
0

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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  • #2
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:
  • #3
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.
 

1. How do I calculate net force using mass, distance, and time?

To calculate net force, you will need to use Newton's second law of motion, which states that force (F) equals mass (m) multiplied by acceleration (a). Therefore, the formula for net force is F = m * a. To find the acceleration, you can use the formula a = Δv/Δt, where Δv is the change in velocity and Δt is the change in time. Once you have the value for acceleration, you can plug it into the formula for net force along with the given mass.

2. What units should I use for mass, distance, and time when calculating net force?

The most common units for mass are kilograms (kg), for distance are meters (m), and for time are seconds (s). However, any consistent units can be used as long as they are converted properly. For example, if the mass is given in grams, it should be converted to kilograms before plugging it into the formula for net force.

3. Can I use net force to calculate the velocity of an object?

Yes, net force can be used to calculate the velocity of an object. You can use the formula v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time. If the object is initially at rest (u = 0), then the formula simplifies to v = at. This can be useful in determining how long it will take for an object to reach a certain velocity when given the net force and mass.

4. Is net force affected by the direction of the force?

Yes, net force is affected by the direction of the force. Net force is a vector quantity, meaning it has both magnitude and direction. This means that forces in opposite directions can cancel each other out, resulting in a net force of zero. It is important to take into account the direction of all forces when calculating net force.

5. How does the distance between two objects affect the net force between them?

The distance between two objects does affect the net force between them. According to Newton's law of universal gravitation, the force of gravity between two objects is inversely proportional to the square of the distance between them. This means that the further apart two objects are, the weaker the force of gravity between them will be. So, the net force between two objects will decrease as the distance between them increases.

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