A 23.0-kg backpack is suspended midway between two trees by a light cord as in Fig. 951. A bear grabs the backpack and pulls vertically downward with a constant force, so that each section of cord makes an angle of 27 below the horizontal. Initially, without the bear pulling, the angle was 15; the tension in the cord with the bear pulling is double what it was when he was not. Calculate the force the bear is exerting on the backpack.
Making Sense of the Universe: Chapter 3 4.1 Describing Motion: Examples from Daily Life How do we describe motion Terms used to describe motion: velocity, acceleration, and momentum. Speed – how far something will go in a certain amount of time. Velocity – the speed and direction of something. Acceleration – when there is a change in speed or direction. Acceleration is not just an increased speed, in science you are accelerating when you are slowing down and speeding up. Also, when you turn around means a change in direction, which therefore means a change in velocity. Galileo pointed out that gravity accelerates all objects by the same amount of time. Air resistance would change the rate of a feather and a rock falling. If you were to drop a feather and a rock on the moon, they would fall at the same rate because there is no air. Momentum and Force Momentum – is the product of its mass and velocity, momentum = mass x velocity. Applying force is the only way to change an object’s momentum. A 2ton truck has much more mass than a bug, which means the truck has much more momentum. Imagine that both the fly and the bug were coming at you in your car head on. When the fly hits your car, nothing much happens to your car. When the truck hits you, it will cause much more damage to your car. The truck has so much more momentum to cause a lot more damage to your car. The sudden change in momentum is a force. Net force – is an overa