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Aim: How do we explain motion along an inclined plane?. Review of the normal force. An object at rest on an Inclined Plane. Label the following forces on the diagram above: ( Ignore the blue lines) Friction Gravity (Weight) Normal Force. Vector Resolution of Weight Force.
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An object at rest on an Inclined Plane Label the following forces on the diagram above: ( Ignore the blue lines) Friction Gravity (Weight) Normal Force
Vector Resolution of Weight Force The weight force can be resolved into two components: One component is parallel to the surface of the incline (mgsinθ) One component is perpendicular to the surface of the incline (mgcosθ)
Effect of angle on motion down an incline Why do objects fall down an incline when the angle is increased? • Mgsinθ increases • Ff decreases because FN decreases because mgcosθ decreases
Skiing Downhill-Problem 1 A 60 kg person on skis is going down a hill sloped at 30 degrees. The coefficient of kinetic friction between the skis and the snow is 0.15. • Draw a freebody diagram. • Find the weight of the skier. • Find the components of the weight of the skier • Find the normal force • Find the force of friction • Find the net force of the skier down the incline. • Find the acceleration of the skier down the incline.
Problem 2 Derive an expression for the angle at which an object of mass m will begin to accelerate down an inclined plane which has a coefficient of µ
Problem 3 • Find the acceleration of this mass. • Find the time it takes the body to slide down the incline
Draw a freebody diagram for an object being pulled up an incline If this load is being pushed up an incline, draw all forces acting on crate. Are there any differences from before? The friction force reverses direction
Problem 4 Object moving up an inclined plane A box is sliding up an incline that makes an angle of 15 degrees with respect to the horizontal. The coefficient of kinetic friction between the box and the surface of the incline is .180. The initial speed of the box at the bottom of the incline is 1.50 m/s. How far does the box travel along the incline before coming to rest?
Problem 5 An pulley system connects an 8 kg mass on an incline to a 16 kg hanging mass. The incline is at an angle of 45 degrees. The coefficient of friction on the incline is 0.23. • What is the acceleration of both masses? • What is the tension in the string connecting both masses?