Download presentation

Presentation is loading. Please wait.

Published byGervais Gregory Modified over 4 years ago

1
Do Now: Do Now: 1. What is the formula to calculate weight? 1. What is the formula to calculate weight? 2. A. Draw the resultant force and calculate it. 2. A. Draw the resultant force and calculate it. B. Calculate the angle. B. Calculate the angle. 7N 5N 7N R = 8.6N Θ=54.5°

2
Aim: How can we calculate forces acting on an object? Free-Body diagrams F app FfFf FNFN FgFg

3
Free-body diagrams – is a sketch that shows all of the forces acting on an object. Free-body diagrams – is a sketch that shows all of the forces acting on an object. Example1: Draw a free-body diagram of the forces acting on a text book sitting on a table. Example1: Draw a free-body diagram of the forces acting on a text book sitting on a table. Normal force – contact force exerted by the surface on the object. (always perpendicular to the surface) Normal force – contact force exerted by the surface on the object. (always perpendicular to the surface) FgFg FNFN

4
Ex2: An.1 kilogram egg is free-falling from a nest in a tree. Neglect air resistance. Ex2: An.1 kilogram egg is free-falling from a nest in a tree. Neglect air resistance. FgFg

5
Ex3: A 50 newton object is suspended motionless from the ceiling by two ropes. Ex3: A 50 newton object is suspended motionless from the ceiling by two ropes. FgFg FTFT FTFT

6
A rightward force is applied to a book in order to move it across a desk. Draw the free-body diagram. A rightward force is applied to a book in order to move it across a desk. Draw the free-body diagram. FgFg FfFf FNFN F app

7
Aim: How can we describe objects in equilibrium? Explain equilibrium in one word. Explain equilibrium in one word. Determine the normal force of a 35 newton object at rest on a table. Determine the normal force of a 35 newton object at rest on a table.

8
How can we define equilibrium? Forces are equal in a specific direction. (x- direction & Y-direction) Forces are equal in a specific direction. (x- direction & Y-direction) Resultant force equals zero. (net force = 0N) Resultant force equals zero. (net force = 0N) Ex: A box has a mass of 10 kg. Calculate the magnitude of the normal force. Ex: A box has a mass of 10 kg. Calculate the magnitude of the normal force. FgFg FNFN

9
Equilibrium At rest At constant velocity F net = 0 Newtons

10
A student pushes a 15 newton box across the table with 20 newtons of force at constant velocity. A student pushes a 15 newton box across the table with 20 newtons of force at constant velocity. ***Constant velocity the net force equals zero*** ***Constant velocity the net force equals zero*** What does “a 15 newton box mean?” What does “a 15 newton box mean?” Sketch a free body diagram. Sketch a free body diagram. Determine the frictional force. Determine the frictional force.

11
A flying bird is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. Draw a free-body diagram. A flying bird is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. Draw a free-body diagram. FgFg F air fric

12
A student holds a 4.5 kilogram object from a string. The object is motionless. Calculate the force of tension in the string. A student holds a 4.5 kilogram object from a string. The object is motionless. Calculate the force of tension in the string. FgFg FTFT

13
Do Now: Do Now: 1. List three ways an object can have acceleration. 1. List three ways an object can have acceleration. A 10 Newton force to the left is applied to a box. Also, a 10 Newton force to the right is applied to the same box. The box must be A 10 Newton force to the left is applied to a box. Also, a 10 Newton force to the right is applied to the same box. The box must be A) at rest A) at rest B) in motion B) in motion C) either in motion or at rest C) either in motion or at rest

14
How can we describe Newton’s 1 st law?

15
Introduction to Newton’s laws of Motion Dynamics – is the branch of mechanics that deals with how the forces acting on an object affect its motion. Dynamics – is the branch of mechanics that deals with how the forces acting on an object affect its motion. An object in dynamic equilibrium moves with constant velocity. That means No NET Force! Net force equals zero. An object in dynamic equilibrium moves with constant velocity. That means No NET Force! Net force equals zero.

16
How can we apply Newton’s first law of motion? A.5 kilogram mass is hanging from a spring. How can we determine the net force? A.5 kilogram mass is hanging from a spring. How can we determine the net force?

17
Equilibrium Static Equilibrium Dynamic Equilibrium Net force zero, object at rest Net force zero, object moving with constant velocity How can we describe the two states of equilibrium?

18
How can we describe inertia? Inertia is the tendency of an object to resist a change in state of motion. Inertia is the tendency of an object to resist a change in state of motion. Mass is used to measure inertia. (kilograms) Mass is used to measure inertia. (kilograms) Inertia and mass are directly proportional. Inertia and mass are directly proportional. Example: The more mass an object has the more inertia the object has. Example: The more mass an object has the more inertia the object has.

19
Newton’s first law of motion – An object at rest will remain at rest and an object in motion (constant velocity) will remain in motion unless acted on by an unbalanced force. Newton’s first law of motion – An object at rest will remain at rest and an object in motion (constant velocity) will remain in motion unless acted on by an unbalanced force. Have you ever experienced inertia in an automobile while it is braking to a stop? Have you ever experienced inertia in an automobile while it is braking to a stop?

20
Describe the following situation using Newton’s first law. Describe the following situation using Newton’s first law. While riding a skateboard (or bicycle), you fly forward off the board when hitting a curb which abruptly halts the motion of the skateboard. While riding a skateboard (or bicycle), you fly forward off the board when hitting a curb which abruptly halts the motion of the skateboard. To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrusted downward at high speeds and then abruptly halted. To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrusted downward at high speeds and then abruptly halted.

21
How can we apply Newton’s 2 nd law? A 6 kilogram box is being pushed with a 25 newton force to the left on a table. The box is moving with constant velocity. A 6 kilogram box is being pushed with a 25 newton force to the left on a table. The box is moving with constant velocity. Sketch free body diagram and label all of the forces. Sketch free body diagram and label all of the forces.

22
How can we define Newton’s 2 nd law? Newton’s second law states when an unbalanced force acts on an object, the object is accelerated in the same direction of the force. Newton’s second law states when an unbalanced force acts on an object, the object is accelerated in the same direction of the force. The net force is NOT zero. NO Equilibrium. The net force is NOT zero. NO Equilibrium. Formula: Formula: F net (sum of forces), m (mass), a (acceleration). F net (sum of forces), m (mass), a (acceleration).

23
Describe the mathematical relationship between acceleration and net force. Describe the mathematical relationship between acceleration and net force. Its acceleration is directly proportional to the net force Its acceleration is directly proportional to the net force Describe the mathematical relationship between acceleration and mass. Describe the mathematical relationship between acceleration and mass. Its acceleration is inversely proportional to the object’s mass Its acceleration is inversely proportional to the object’s mass

24
A 5 kilogram box is pushed with a 20 newton force to the right on a frictionless surface. Determine the acceleration. A 5 kilogram box is pushed with a 20 newton force to the right on a frictionless surface. Determine the acceleration. A 2 kilogram box at rest accelerates to a speed of 10 meters per second in 2 seconds. Calculate the net force. A 2 kilogram box at rest accelerates to a speed of 10 meters per second in 2 seconds. Calculate the net force.

25
How can we determine the net force?

26
Determine net force using a picture Example 1: A 2kg block is sitting on a table. A 10 N force is applied to the right and a 45 N force is applied to the left. Example 1: A 2kg block is sitting on a table. A 10 N force is applied to the right and a 45 N force is applied to the left. A) Determine the net force acting on the block? A) Determine the net force acting on the block? B) Calculate the acceleration. B) Calculate the acceleration. F net in the x direction is the difference between the two forces acting in the x direction. to the left

27
Refer to example 1: The net force acting on the box is 20 Newtons to the right. The net force acting on the box is 20 Newtons to the right. Calculate the acceleration. Calculate the acceleration. to the left

28
A 20 newton force is applied to a 4 kilogram object to the right accelerating it at 4.5 meters per second 2. A 20 newton force is applied to a 4 kilogram object to the right accelerating it at 4.5 meters per second 2. A) Determine the net force. A) Determine the net force. B) Calculate the frictional force. B) Calculate the frictional force.

29
A person pushes a 7.0 kg box on a frictionless surface. The box accelerates 5 m/s 2. Calculate the applied force on the box. A person pushes a 7.0 kg box on a frictionless surface. The box accelerates 5 m/s 2. Calculate the applied force on the box. to the right

30
How can we use Newton’s 2 nd law to solve motion problems? Define Newton’s 1 st law. Define Newton’s 1 st law. Sketch the equilibrium diagram. Sketch the equilibrium diagram. Determine the net force on an object when it is moving with constant velocity. Determine the net force on an object when it is moving with constant velocity. A 3 kilogram chair is being push with a 10- newton force to the right. Sketch a free body diagram. A 3 kilogram chair is being push with a 10- newton force to the right. Sketch a free body diagram.

31
Cart demonstration As mass decreases, acceleration _____________. As mass decreases, acceleration _____________. How would you sketch a graph of acceleration vs. mass? How would you sketch a graph of acceleration vs. mass?

32
A 50 newton force is required to accelerate a 3.5 kilogram object at 8.6m/s 2 over a level floor. A 50 newton force is required to accelerate a 3.5 kilogram object at 8.6m/s 2 over a level floor. A) Sketch a free body diagram. A) Sketch a free body diagram. B) Determine the net force B) Determine the net force C) Calculate the magnitude of the frictional force acting on the object C) Calculate the magnitude of the frictional force acting on the object

33
A 6.5 kilogram object is accelerating at 8.0 meters per second 2. The magnitude of the frictional force is 10 newtons. A 6.5 kilogram object is accelerating at 8.0 meters per second 2. The magnitude of the frictional force is 10 newtons. A) Sketch a free body diagram. A) Sketch a free body diagram. B) Determine the net force. B) Determine the net force. C) Calculate the applied force. C) Calculate the applied force.

34
**A constant 3,000 newton frictional force is acting on a 1200 kilogram car. The car is brought to rest in 20 seconds. **A constant 3,000 newton frictional force is acting on a 1200 kilogram car. The car is brought to rest in 20 seconds. A) Identify the net force. A) Identify the net force. B) Calculate the deceleration. B) Calculate the deceleration. C) Calculate the initial velocity of the car. C) Calculate the initial velocity of the car.

Similar presentations

© 2020 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google