 Let's solve a question on tension. Here we have a person who uses a rope to climb a tree and the mass of the person is 70 kilograms. Find the tension in the rope when the person comes down with an acceleration of two meters per second square and we can assume that the rope is massless. As always, hit pause and try this one on your own first. Alright, hopefully we have given this a shot. Now in this one we know that the person is coming down with an acceleration of two meters per second square. So if we draw, if we try to model the person with just a point object, we know that the acceleration here, the acceleration here this is two meters per second square and we also know the mass of the person which means we know the weight. We can write the weight as we know that weight is this is w equals to mg. So this would be 70 into 10. We can take g as 10. This would be 700 Newtons. So there will be a force in the downward direction. We draw that again. This will be 700 Newtons and we are trying to draw the free body diagram of the person because we know the acceleration with which the person is coming down. So it's better that we draw the free body diagram of the person. We also know the weight. We need to figure out the tension in the rope. Now could the tension be down or could it be up? There are two questions that come. We know that the person is holding the rope. So could the tension be like this? Let me draw it like this. Should the tension be like this or should it be should it be like this? That is the question. Now turns out that tension only pulls up the person. It can never push down a person and we can try and understand that. Let's say we have some person here and they are pushing. Rather they are pulling. They are pulling a box. They are pulling a box which is kept like this attached to a rope and they are pulling the block towards themselves. They are pulling the block towards themselves. So now if we try to draw the free body diagram of the rope, we know that the rope is definitely experiencing a force from the person which is in this direction because the rope is experiencing a pull from this end. The person is pulling the rope at this end. Now if we draw the free body diagram of the person, according to Newton's third law, there will be an equal and opposite force to this force right here and that will be to the right which is acting on the person. This will be the tension force that the rope is exerting on the person. So the tension force is always away from the object from the mass and in this case from the person. So it's never really acting down. Tension can never push down. It can only pull up. It can only pull the object. So we remove this one. The tension force really is just the force which is acting in the upward direction and now what we can do is we can use Newton's second law which states that the net force acting on a body, this is equal to MA. So here the net force really is 700 minus T and we are writing 700 minus T because the person is moving down right. So that means this force 700, it must be more than T. So 700, this is 700 minus T. 700 minus T. This is equal to 70 into acceleration which is 2. 70 is the mass. So this becomes 140. When we take T to the right hand side, this will be T. This is equal to 700 minus minus 140 and when you work this out, T comes out to be equal to 560 Newton's. So this is 560 Newton's.