Speed, Velocity, & Acceleration
Which quantity describes how fast an object is moving without regard to direction?
Speed
Which Newton’s Law explains why passengers move forward when a car suddenly stops?
Newton’s First Law (inertia)
What force keeps a book resting on a table from falling through it?
Normal force
An object moves at 5 m/s for 10 s. What distance does it travel?
➡️ 50 m
What property of matter describes resistance to changes in motion?
Inertia
What physical quantity describes the rate at which velocity changes over time?
Acceleration
If the net force on an object is zero, what happens to its motion?
It remains at rest or moves at constant velocity
Which force always acts opposite the direction an object is sliding or trying to slide?
Friction
An object accelerates from rest at 2.0 m/s² for 6.0 s. What is its final velocity?
12 m/s
Does mass change when an object is taken from Earth to the Moon?
No
An object moves at a constant speed of 12 m/s for 20 s. How far does it travel?
240 m
A 10 kg object experiences a net force of 50 N. What is its acceleration?
5 m/s²
A box is pushed across frictionless ice and then released. What horizontal force is needed to keep it moving?
Zero
A car slows from 20 m/s to rest with an acceleration of –4 m/s². How long does it take to stop?
5 s
Why do airbags reduce injuries during car crashes?
They increase collision time, reducing force
An object thrown straight upward has zero velocity at the top. What is its acceleration at that point?
–9.8 m/s² (downward)
If the force on an object stays the same but its mass doubles, what happens to the acceleration?
It is cut in half
A 20 N force acts to the right and a 50 N force acts to the left. What is the net force?
30 N to the left
An object accelerates from rest and reaches 16 m/s after traveling 64 m. What was its acceleration?
2.0 m/s²
A ball reaches the top of its trajectory. What forces act on it at that instant?
Only gravity
Two objects are dropped from rest at the same time. One is thrown downward. Ignoring air resistance, which hits the ground faster and why?
The thrown one hits first because it starts with greater initial velocity, but both have the same acceleration.
A fly collides with a moving truck. Compare the forces acting on the fly and the truck.
They experience equal and opposite forces (Newton’s Third Law)
A person lifts a backpack upward at constant speed. What is the net force on the backpack?
zero
A ball is thrown straight upward and returns to the same point after 8.0 s. What was its initial velocity?
39.2 m/s upward
Two projectiles are launched at the same speed, one at 30° and one at 45°. Which travels farther horizontally and why?
45° travels farther because it maximizes range