Gravity — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. When an object falls, gravity makes it speed up, or accelerate.
Gravity adds about 9.8 m/s of downward speed each second during free fall.
2. Air pushing back on a falling object is called air resistance.
Air resistance opposes motion through the atmosphere.
3. The greatest speed a falling object can reach in air is its terminal velocity.
Terminal velocity is the steady speed where gravity and air drag balance.
4. At terminal velocity, the falling object stops accelerating because forces are balanced.
Equal upward drag and downward gravity yield zero net force.
5. A skydiver reaches a higher terminal velocity when she pulls her arms in to be more streamlined.
Less surface area means less air drag, so terminal velocity is higher.
6. On the Moon, there is no atmosphere, so a feather and hammer fall at the same rate.
With no air resistance, all objects accelerate equally under gravity.
7. The unit scientists use for acceleration is meters per second per second.
Acceleration units are m/s squared, or meters per second per second.
8. Earth's gravitational acceleration is about 9.8 meters per second squared.
Standard gravity near Earth's surface is about 9.8 m/s squared.
9. When a parachute opens, air resistance grows quickly, so terminal velocity decreases.
Greater area gives more drag, balancing gravity at a lower speed.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Acceleration
→ Rate at which speed changes
Falling with only gravity acting
Air resistance
→ Frictional force from the atmosphere
Frictional force from the atmosphere
Terminal velocity
→ Steady top speed of a falling object
Steady top speed of a falling object
Free fall
→ Falling with only gravity acting
Rate at which speed changes
Acceleration is rate of speed change, air resistance is air drag, terminal velocity is steady max speed, free fall is gravity-only motion.