Post on 30-Dec-2015
description
Free-body Diagram
Homework
To a 10.0-kg table, three forces were applied on it.
F1 = 5.00 N, South
F2 = 6.00 N, East
F3 = 4.00 N, West
1. Using the component method, what is the net force applied on the table?
Homework
To a 10.0-kg table, three forces were applied on it.
F1 = 5.00 N, South
F2 = 6.00 N, East
F3 = 4.00 N, West
2. If a fourth force was applied and made the net force zero, what is the magnitude and direction of this fourth force?
Homework
Provide the FBD of the system (in red text) in the following scenarios and identify the agents of all forces cited.
1. a stone in midair after thrown upwards
2. a balloon-powered car moving at a constant speed
3. a balloon-powered car moving with a completely deflated balloon
Homework
• A certain balloon-powered car has a mass of 50.0 grams. The gushing air from its balloon provides a thrust force of 0.30 Newton. If the car is accelerating at 2.00 m/s2 for the first 5.00 meters, do you think friction is acting on the car? Defend your answer by showing your solutions.
Objectives
• Recall the Laws of Motion. • Construct the free-body diagram of the
forces acting on a body. • Determine the magnitude of forces acting
on a body.
Laws of MotionIn memory of the past lesson…
Can you remember?
What are the three laws of motion
proposed by Einstein?
Can you remember?
What are the three laws of motion
proposed by Isaac Newton?
What law has this provision?
For every action, there is an equal but
opposite reaction.
What law has this provision?
Every body continues in its state of rest, or of motion in a straight line
at constant speed, unless it is compelled to change that state by a
net force exerted upon it.
What law has this provision?
The acceleration produced by a net force on a body is directly
proportional to the magnitude of the net force, is in the same direction as the net force, and is inversely proportional to the mass of the
body.
Free-body Diagram
Balloon-powered Cars
ALIN ANG NAIBA?
Balloon-powered Cars
As the air is expelled from the balloon, the car moves. What are the forces acting on it?
Free-body Diagram
A free-body diagram is a physical model that represents all forces acting on a system.
Some Types of Forces
• Weight - the gravitational pull of the earth
• Friction - the contact force that acts to oppose sliding motion between surfaces
• Normal - the contact force exerted by a surface on an object
• Thrust - a general term for the forces that move objects
Read p. 94 of Glencoe for the complete list.
When constructing the FBD,
Always identify the SYSTEM.
Balloon-powered Cars
As the air is expelled from the balloon, the car moves. What are the forces acting on it?
Balloon-powered Cars
As the air is expelled from the balloon, the car moves. What are the forces acting on balloon-powered car?
How would one know that a force should be in the FBD?
For every force there should be
an AGENT.
How would one know that a force should be in the FBD?
If you cannot identify the agent that applies or causes
the force, then that force should not be part of the
FBD.
Balloon-powered Cars
What are the agents applying these forces?
Qualitative FBD
.
Quantitative FBD
• Construct the FBD.
MassesBear = 120 gTable = 12 kg
355 g
125 g
25.0 kg1. Determine the magnitude of the weight (in Newton) of the following:
a. starb. blue pillowc. table
W = 1.23 N
W = 3.48 N
W = 245 N
355 g
125 g
25.0 kg2. Determine the normal force acting on the following:
a. starb. blue pillow c. table
Fn = 1.23 N
Fn = 4.70 N
Fn = 250. N
Simple Drills
F applied = 20.0 N
f = 20.0 N
Describe the direction of the system if it is at rest.
Simple Drills
F applied = 20.0 N
f = 20.0 N
Describe the velocity of the system if it is at rest.
Simple Drills
F applied = 20.0 N
f = 20.0 N
Describe the velocity of the system if it is moving 30 m/s.
Simple Drills
F applied = 20.0 N
Describe the direction of the system if it is moving.
Simple Drills
F applied = 20.0 N
Describe the velocity of the system if it is moving.
Seatwork
• Use a piece of size 4. • Listen to the instructions carefully.
Number 1
f = 15.0 N
Describe the motion of this body moving to the right. (speeding up, slowing down, constant velocity)
Number 2
f = 15.0 N
Describe the motion of this body moving to the right. (speeding up, slowing down, constant velocity)
F applied = 20.0 N
Number 3
f = 15.0 N
What is the net force acting on the body (magnitude and direction)?
F applied = 20.0 N
Number 4
f = 15.0 N
If the body has a mass of 5.00 kg, what is its acceleration (magnitude and direction)?
F applied = 20.0 N
Number 5
f = 15.0 N
How many seconds will it take for this body to increase its speed by 5.00 m/s?
F applied = 15.0 N
End of Session