Helping My Autistic Son with Momentum and Friction in a Dog's Movement

[Sgt]

Homework Statement

I don't know how to use this forum so here we go. My 16 year old autisitc son is stumped with this question. If anyone can help me send him in the right direction it would be great, I am lost.

dog with a mass of 113 g runs to the right at 2.00 m/s, sees a mouse stopes using paws, slides 80.0 cm during deceleration, dog turns and runs other direction, calculate the magnitudes of change in dog's momentum AND the average frictional force that brings about this change.

He can't figure out what formula to use and I have no idea, can anyone point me in the right direction?

what happened to 2+2=4?

Homework Equations

The Attempt at a Solution

total 1^p=0
slow down segment = 0.226ns
run in opposite direction segment = 0.226ns

help?

 

[badreligion]

Magnitude of the change in the dog's momentum basically means an Impulse. Which can be figured out using the formula J=FΔt.

J=Impulse aka the answer to the first question
F=force
Δt= Change in time

You have Δt but still need force.

F=ma

m=mass
a=acceleration

You have mass but still need acceleration

a=Δv/t

Δv=change in velocity
t=time

Hopefully you can work that out good luck and I will still be online for more question

 

[thomate1]

Hi there,

First of all, I want to commend you for trying to help your son with this question. It's great to see a parent so involved in their child's education.

To answer the question, we need to use two main equations: Newton's second law, which states that the net force on an object is equal to its mass multiplied by its acceleration, and the definition of momentum, which is mass multiplied by velocity.

For the first part of the question, we need to calculate the change in momentum of the dog as it stops and changes direction. To do this, we can use the equation:

Δp = mΔv

Where Δp is the change in momentum, m is the mass of the dog, and Δv is the change in velocity. In this case, the dog's initial velocity is 2.00 m/s, and its final velocity is 0 m/s (since it stops). So, Δv = 0 - 2.00 = -2.00 m/s. Plugging in the values, we get:

Δp = (0.113 kg)(-2.00 m/s) = -0.226 kg m/s

So, the magnitude of the change in momentum is 0.226 kg m/s.

For the second part of the question, we need to calculate the average frictional force that brings about this change in momentum. To do this, we can use Newton's second law again, but this time we need to solve for the force:

F = mΔv/Δt

Where F is the force, m is the mass of the dog, Δv is the change in velocity (which we already calculated), and Δt is the time it takes for the dog to stop and change direction. We can find Δt by dividing the distance the dog slides (80.0 cm) by its initial velocity (2.00 m/s):

Δt = (80.0 cm)/(2.00 m/s) = 0.4 s

Now, plugging in the values, we get:

F = (0.113 kg)(-2.00 m/s)/(0.4 s) = -0.565 N

So, the average frictional force that brings about the change in momentum is 0.565 N.

I hope this helps your son with his homework. If he has any further questions, I would recommend consulting his