physics chapter 3 review

An object in free fall has a constant ____________(1), but its ________(2) changes.

1. acceleration 2. velocity

At Earth's surface, how much force does gravity exert on a 1- kilogram object?

9.8 N

If all objects in free fall accelerate at the same rate, why does a feather fall slower than a baseball?

A feather falls slower than a baseball because air resistance exerts a force opposite to the direction of the feather's motion. Because the weight of a feather is spread out over a larger area, the feather has to push a lot of air out of the way as it falls. As a result, the force of air resistance is close in magnitude to the weight force but in the opposite direction. The net force acting on the feather is small, so the acceleration is much less than 9.8 m/s2

Write the definition of acceleration due to gravity. What letter is used to represent this value?

Acceleration due to gravity is the acceleration of an object that is caused by gravity and is equal to 9.8/ m/s2 on Earth's surface. The letter g is used to represent this value.

Define air resistance

Air resistance: is a force that acts against the force of gravity on an object in free fall.

Why would an astronaut weigh less on the moon, even though his or her mass does not change?

An astronaut weighs less on the moon because the Moon's gravitational force is weaker than Earth's

A ball thrown upward is in free fall beginning at this moment

As soon as it leaves the thrower's hand.

Write the equation for free fall distance. Label each variable in the equation as shown on page 66.

D = vogt (distance = average velocity x time)

What is free fall?

Freefall is the acceleration of a falling object due to Earth's gravity.

Write the equation for finding an object's weight if you know its mass and the strength of gravity. Label each variable in the equation as shown on page 67.

Fw = mg (mass x strength of gravity)

Name two examples of objects moving through the air but not in free fall.

Sample answers: An airplane in flight and a bumblebee in flight are not in free fall because another force in addition to gravity is acting on them.

Name two examples of objects moving through the air in free fall.

Sample answers: an apple that drops from a tree and a kicked soccer ball are in free fall until they hit the ground

What is terminal velocity?

Terminal velocity is the maximum velocity reached by an object in free fall. At this point the forces of gravity and air resistance are equal.

Explain how to find the weight of an object on Earth if you know the object's mass in kilograms.

To find the weight of an object on the Earth's surface, multiply its mass in kilograms by 9.8 N/kg.

Write the equation for free-fall velocity. Label each variable in the equation as shown on page 63.

V = gt (velocity = acceleration due to gravity x time)

Write the equation for the average velocity of an object in free fall. Label each variable in the equation as shown on page 65.

Vavg = vf + vi / 2 (average velocity = final velocity + initial velocity divided by 2)

The force of gravity acting on an object is called

weight