Position and Motion
What is the location of an object called?
Its position.
What are the units of speed?
Distance per unit of time (e.g., m/s, km/h, mph).
What is a force?
Any push or pull.
What are balanced forces?
Forces that act on an object without changing its motion; they add up to zero.
What is gravity?
A noncontact force that pulls objects toward each other.
What is a change in an object's position called?
Motion.
How is velocity different from speed?
Velocity includes direction; speed does not.
What can a force cause an object to do?
Start moving, change direction, speed up, slow down, or stop.
What is inertia?
The tendency of an object in motion to stay in motion, or an object at rest to stay at rest.
What is friction?
A force between surfaces that slows objects or stops them from moving.
Name three things needed to fully describe motion.
Distance, direction, and time.
Which is fastest: giraffe (14 m/s), eagle (33 m/s), horse (21 m/s), or cheetah (30 m/s)?
The eagle, at 33 m/s (73.8 mph).
What two factors affect the acceleration of an object?
The amount of force acting on it, and the weight (mass) of the object.
What is the net (total) force on an object?
The sum of all forces acting on it.
What two factors affect the gravitational pull between two objects?
The amount of mass in the objects and the distance between them.
If an object moves 12 km in one hour on a bike, what is its speed?
12 km/h
A plane travels 640 km south in 2 hours. What is its average velocity?
320 km/h south.
If the same force is applied to two objects of different weights, which accelerates more slowly?
The heavier object accelerates more slowly.
If the total force on an object equals zero, what happens to its motion?
The object will not accelerate — it stays at rest or keeps moving at the same speed and direction.
Why does a feather fall slower than a pencil (in air)?
Air resistance acts on the feather more, slowing it down. Without air, both would fall at the same rate.
What does it mean if a plane's average velocity is 320 km/h south for 2 hours?
It flew 640 km south in 2 hours — velocity includes both speed AND direction.
If a moving object changes direction while keeping the same speed, is it accelerating? Why?
Yes — because the direction of velocity changes, it is still accelerating.
What is the difference between a contact force and a noncontact force? Give one example of each.
Contact forces require objects to touch (e.g., a bat hitting a baseball); noncontact forces act without touching (e.g., gravity).
Explain how unbalanced forces affect a skateboarder who is at rest on a slope.
An unbalanced force causes her to start moving. Unbalanced forces can continue to change her speed and direction.
Explain how both gravity and friction would affect a roller coaster car.
Gravity pulls the car down hills, increasing its speed. Friction between the wheels and track slows the car, eventually bringing it to a stop.