Relative Motion

Observers using different ___________________ may measure different velocities for an object in motion

• frame of reference

• relatives of motion

• projectile motions

• constant velocity

What is Relative?

• Relative means opposite

• Relative means in comparison of something else

If a car passes you in the left lane going 90 km/hr north while you are driving 80 km/hr north, how fast is the car moving relative to your car?

• 170 km/hr

• 90 km/hr

• 80 km/hr

• 10 km/hr

A boat heading north crosses a wide river with a velocity of 10.00 km/h relative to the water. The river has a uniform velocity of 5.00 km/h due east. Determine the boat’s speed with respect to an observer on shore. (Hint: draw vector arrows - you should get a right triangle)

• 11.18 km/hr

• 15 km/hr

• 5 km/hr

• 30 km/hr

A dog and a cat are about to fight, running towards each other, both at 12 m/s. What are their velocities relative to each other?

• 12 m/s

• 24 m/s

• 0 m/s

• 6 m/s

A passenger at the rear of a train traveling at 15 m/s relative to the ground throws a baseball with a speed of 15 m/s in the direction opposite the motion of the train. What is the velocity of the baseball relative to the ground as it leaves the thrower’s hand? In other words: how fast does a person on the ground see the ball move?

• 30 m/s

• 15 m/s

• 0 m/s

• 20 m/s

A woman on a bicycle travels at 9 m/s relative to the ground as she passes a little boy on a tricycle going in the opposite direction. If the boy is traveling at 1 m/s relative to the ground, how fast does the boy appear to be moving relative to the woman?

• 9 m/s

• 8 m/s

• 0 m/s

• 10 m/s

What is the walker's speed from the observer's perspective?

• 10 mph

• 40 mph

• 50 mph

• 30 mph

What is the walker's speed with respect to the train?

• 30 mph

• 10 mph

• 40 mph

• 50 mph

For us humans, what is our basic reference frame?

• Earth

• The Sun

• The Universe

• The Milky Way Galaxy