A new equipment arrived to the EPCC Makerspace. The box is...

A new equipment arrived to the EPCC Makerspace. The box is being pushed and pulled with forces F?=450 N and F?=400 N, as shown in the picture. Calculate the distance it slides in order to gain a speed of 8 m/s (starting from rest). The coefficient of kinetic friction between the box and the surface is \(\mu_k\)=0.2. The mass of the box is 140 kg

Transcript

00:03 Right.

00:03 Looks like your question is about work and change in energy and how it's related to each other.

00:11 So work can be defined in a couple of ways.

00:15 We can define it as force times distance, or we can define it as change in energy.

00:21 So i'll put both of us down.

00:23 Work is equal to f times d or force times distance.

00:27 Or work is the change in energy, whatever energy we're looking at.

00:35 So this exercise is kind of walking you through how do you use the work equations to solve for unknown information, such as how fast is this object going to be going at the end? so part a, they give us some information in the drawing.

00:55 So they tell us that the force is 7 .1 newtons.

01:02 So that's for that first blank.

01:04 They also tell us the mass is 1 .2 kilograms.

01:08 That's not necessary for this first part yet.

01:11 They do tell us what the angle is.

01:14 Well, in the drawing, you can tell that it's zero degrees.

01:18 It's being pulled straight parallel to the table.

01:21 So the angle is zero.

01:24 And the distance was also given in the problem.

01:30 It was 183 centimeters.

01:32 So i'm going to change that to meters, 1 .83 meters.

01:36 I did forget my cosine theta on my equation up here, which might come into play on a problem where there is an angle on the pole, but on this one at zero.

01:56 So that allows us to find the work to be done.

01:59 So that's in part b.

02:02 The work is equal to the force times the distance.

02:06 Cosine theta is one.

02:07 So i'm going to just leave that off in this scenario.

02:10 So i have a 7 .1 times.

02:13 The distance of 1 .83, which i do need to have in meters for me to get jewels for the answer.

02:22 So i get 13 joules for an answer.

02:25 So the main thing there is to convert and then know that it's force time to distance.

02:30 And with the angle being zero, cosine zero is one.

02:34 So we didn't need to do anything with that part.

02:40 So it just comes down to force times distance for the work.

02:44 Now, part c is filling out a little table here.

02:50 So we have three different forms of energy in the mechanical energy world.

02:57 So we've got kinetic energy, gravitational potential energy, and elastic potential energy.

03:05 Well, is the kinetic energy changing? it definitely is because there's a force being applied.

03:10 So the force is changing the volume.

03:16 Velocity...

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