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