Terms and Definitions
Define velocity
The speed and/or direction of an object.
An object falls for 9 seconds. What is its velocity before it hits the ground?
88.2 m/s
A skydiver who weighs 700 N downwards reaches a constant velocity.
a. What is the force of the air resistance of the skydiver?
b. What is the net force?
a. 700 N upwards
b. 0 N
A car travels 9 m in 6 seconds. What was its velocity?
1.5 m/s
Who is the father of experimental science?
Galileo Galilei
Define acceleration
The rate of change of the speed and/or direction of an object. The change in velocity over time.
An object is thrown off the top of a tower. It falls for 13 seconds before it hits the ground. How tall is the building?
828.1 m
Two people work together to move a box. The box moves at a constant speed. The friction force working against the box is 900 N right. One person pulling the box pulls with a force of 300 N left. How hard is the other person pulling the box?
600 N left.
Someone kicks a ball across the asphalt on a playground from rest. Is travels for 8 seconds at 34 m/s. What was the ball's acceleration?
4.25 m/s2
A ball is thrown upwards. Neglect air resistance. At the top of its path, what is its acceleration?
Define freefall
An object falling under the effect of gravity only, without air resistance.
A 67 g object falls from a cliff in freefall. What is its force?
656.6 N
A painter is painting up on a scaffold, suspended static against the building. The scaffold itself weighs 700 N. The painter weighs 500 N and the paint can and other small items add up to 100 N. One side of the scaffold is held up by a rope with a force of 600 N. What is the force of the rope on the other side?
700 N upward.
A scooter travels at 150 m/s. In 7 seconds, it slows to 90 m/s. What was the scooter's acceleration?
-8.57 m/s2
Demonstrate the difference between a variable and a unit.
A variable is what you see in a formula. A unit is what goes after the number to tell you what kind of information it is.
Ex: v is the variable for velocity (v=gt), while m/s is the unit for velocity (60 m/s).
When the net force is equal to 0
An object falls off a cliff for 9 seconds. How far did it fall?
396.9 m
A 65 g object hurdles through the air, accelerating at 7 m/s2. What is the force of the object?
455 N
A car travels 102 m in 12 seconds. What was the velocity of the car?
8.5 m/s
What are three ways to accelerate?
Speed up, slow down, or change direction.
Define inertia
An object's resistance to change while it is in motion.
In freefall, a falling object has a force of 68 N. What is its mass?
6.94 g
A 20 kg object has a force of 34 N being exerted on it. What is its acceleration?
1.7 m/s2
An airplane goes from flying 160 m/s to 250 m/s in 20 seconds. What was its acceleration during this time?
4.5 m/s2
The acceleration of an object is directly proportional to the net force exerted on it and inversely proportional to the mass (F=ma).