Motion
Movin and Groovin!
Frame of Reference
• Movement from a fixed point.
• Movement is relative to a fixed point.
• Is she moving towards you or away from you?
Frame of Reference
• What is the space shuttle’s frame of reference?
• What is the race car’s frame of reference?
Frame of Reference
• Are we moving right now???
• Yes! The Earth rotates at about 1000 miles per hour.
Speed
• Speed is a measure of how fast something is moving.
• Speed = Distance
Time
Average Speed
• On trips our speeds usually fluctuate.
• The average speed is usually much different than our instantaneous speeds.
• Average Speed = total distance traveled
total time
Example
• If a cheetah runs 25m/s, how far will the cheetah run in 10 seconds?
S=d/t d= speed x time
d= 25m/s x 10s = 250m
Velocity
• What’s the difference between speed and velocity?
• Speed = how fast something moves
(30 m/s)
• Velocity = how fast something moves in a direction (30 m/s east)
Velocity
• velocity = distance
time
Constant Velocity
• Constant velocity = constant speed and constant direction
• Does velocity change when a car goes around a curve?
• If a train and a car are traveling the same path at the same speed, which is more difficult for Superman to stop? Why?
Momentum
• Objects with more momentum would be more difficult to stop.
• Momentum depends on velocity and mass.
momentum = mass x velocity
p = m x v
Acceleration
• Any change in velocity is known as acceleration.
• Acceleration = final velocity – initial velocitytime
a = Δ v Δ t
Acceleration• What does an acceleration tell you?
• If the acceleration is small, the speed is increasing gradually.
• If the acceleration is great, the object is speeding up rapidly.
• Negative acceleration (deceleration) means that the object is slowing down.
Acceleration
• Acceleration is determined by a velocity-time graph
Practice Problems
• Natalie accelerates her skateboard along a straight path from 0 m/s to 4.0 m/s in 2.5 s. What is her acceleration?
a = 4.0 m/s – 0 m/s
2.5 s
a = 1.6 m/s2
Practice Problems
• A turtle swimming in a straight line toward shore has a speed of 0.50 m/s. After 4.0 s, its speed is 0.80 m/s. What’s the turtles average acceleration?
a = 0.80 m/s – 0.50 m/s4.0s
a = 0.075 m/s2
Force
• What is force?
• Force is the change in velocity or acceleration of an object.
Force
• What is a balanced force?
• Forces that cancel each other out to produce zero net force.
Force
• What is an unbalanced force?
• Forces that combine to cause an object to accelerate.
Friction
• What is friction? How does it effect motion?
• Friction is the force between two objects in contact that opposes the motion of either object.
Friction