Relative Motion and Reference Points

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

• frames of reference

• relatives of motion

• projectile motions

• constant velocity

If a car passes you 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 passenger at the rear of a train traveling at 15 m/s relative to Earth 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 Earth as it leaves the thrower’s hand?

• 30 m/s

• 15 m/s

• 0 m/s

• 20 m/s

A spy runs from the front to the back of an aircraft carrier at a velocity of 3.5 m/s. If the aircraft carrier is moving forward at 18.0 m/s, how fast does the spy appear to

be running when viewed by an observer on a nearby stationary submarine?

• 14.5 km/hr

• 14.5 m/s

• 21.5 m/s

• 63 m/s

Which statement describes a vector?

• It has magnitude but no direction
• It has direction but no magnitude
• It has both direction and magnitude
• It has constant magnitude but no
   direction

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

A train is travelling 50 m/s north on a track. A passenger on the train walks to the bathroom 1 m/s to the north. What is the speed of the passenger relative to the train?

• 1 m/s

• 51 m/s

• 49 m/s

• 50 m/s

A dog and a cat are at a stand-off, running towards each other, both at 12 m/s. What is the magnitude of velocity of the cat relative to the dog?

• 12 m/s

• 24 m/s

• 0 m/s

• 6 m/s

A place or object used for comparison to determine if another object is in motion is called a

• comparison point
• reference point
• point of view
• motion detector

Acceleration is

• increasing speed
• decreasing speed
• changing direction
• all of the above