Uniform Motion and Relative Motion SPH3U UNIT 1: KINEMATICS

Warm-up: Review Questions True / False ______ Uniform motion is movement in a straight line at a constant speed. ______ Most motion is uniform. ______The position-time graph for uniform motion will be a straight line with a positive slope. ______ uniform motion is also known as accelerated motion.

Warm-up: Review Questions True / False ___T___ Uniform motion is movement in a straight line at a constant speed. ___F____ Most motion is uniform. ___T___The position-time graph for uniform motion will be a straight line with a positive slope. ___F___ uniform motion is also known as accelerated motion.

Recall: Uniformly accelerated motion  ** Non-uniform motion, by default, is accelerated motion. Accelerated motion occurs when we have a change in speed or direction or both.  Uniformly accelerated motion is when an object is travelling in a straight line and changes its speed uniformly with time.

Recall: Uniformly accelerated motion  Uniformly accelerated motion (also known as uniform acceleration) will have a straight line (positive or negative slope) on a v-t graph and a horizontal straight line on an a-t graph.

Recall: Uniformly accelerated motion  Uniformly accelerated motion (also known as uniform acceleration) will have a straight line (positive or negative slope) on a v-t graph and a horizontal straight line on an a-t graph.

Recall: Uniformly accelerated motion  ** In this course, we only examine things that have uniform acceleration.  Ex. Falling objects  ** Instantaneous acceleration is acceleration at a particular instant in time. For uniform acceleration, instantaneous acceleration always equals average acceleration.

Relative Motion  When we observe motion, we are always measuring it with reference to some particular frame.

Relative Motion a) How fast does the person in the car measure the truck to be going? b) How fast does the person in the car measure the person on the street to be going? The velocity of a body relative to a particular frame of reference is called relative velocity.

Relative Motion a) How fast does the person in the car measure the truck to be going? 20 km/h [East] b) How fast does the person in the car measure the person on the street to be going? 30 km/h [West] The velocity of a body relative to a particular frame of reference is called relative velocity.

Relative Motion

Using a relative velocity equation

Relative Motion

More Examples 1) A girl sitting at a bus stop sees a bus go by her at 20km/h [W]. A man inside the bus get up and starts to walk towards the back of the bus. The man walks at 2km/h [E] relative to the bus.  How fast is the man moving relative to the girl?

Relative Motion

2) A child rolls a ball across a boat at a velocity of 4 m/s [N] (relative to the boat). If the boat is travelling at 6m/s [W] relative to the shore, what is the velocity of the ball relative to the shore?

Relative Motion

2) A child rolls a ball across a boat at a velocity of 4 m/s [N] (relative to the boat). If the boat is travelling at 6m/s [W] relative to the shore, what is the velocity of the ball relative to the shore? 4 m/s 6 m/s θ

Homework Extra Practice with Relative Motion: Homework  Do the questions below and also do pg. 23 # 6,7 and pg. 24 # 5 1) Determine the velocity of a bird relative to the ground if the velocity of an airplane relative to the ground is 200km/h [E] and the velocity of the bird relative the plane is 195 km/h [W]. 2) A kite is floating through the air at a velocity of 2km/h [E] relative to the air. If the wind speed is 10 km/h [N] relative to the ground, what is the velocity of the kite relative the ground?