MOTION BASICS
What is the difference between distance and displacement?
Distance is the total path traveled. Displacement is the change in position from the starting point to the ending point and includes direction.
What does it mean for an object to accelerate?
Its velocity changes over time. It can speed up, slow down, or change direction.
What is a force?
A push or a pull.
Which of Newton’s Laws is also known as the Law of Inertia?
Newton’s First Law.
What two quantities determine an object’s momentum?
Mass and velocity.
A runner travels 60 m east, then 20 m west. What are the runner’s total distance and displacement?
Distance = 80 m. Displacement = 40 m east.
A car’s velocity changes from 10 m/s to 20 m/s in 5 seconds. What is its acceleration?
2 m/s².
A box has a 12 N force pushing right and a 7 N force pushing left. What is the net force?
5 N to the right.
A balloon flies forward when air shoots backward out of it. Which Newton’s Law explains this?
Newton’s Third Law.
A 4 kg object travels at 3 m/s. What is its momentum?
12 kg·m/s.
A car travels 150 km in 3 hours. What is its average speed?
50 km/h.
On a distance-time graph, what does a steeper slope tell you about the object’s motion?
The object is moving faster.
A book is sitting motionless on a table. What two main forces are acting on it, and why does it not accelerate?
Gravity pulls downward and the normal force pushes upward. The forces are balanced, so the net force is 0 N.
A 10 kg object experiences a net force of 30 N. What is its acceleration?
3 m/s².
A force of 20 N acts on an object for 3 seconds. How much impulse is delivered?
60 N·s.
A student walks 30 m east, 10 m west, then 20 m east in 20 seconds. Find the total distance, displacement, average speed, and average velocity.
Distance = 60 m. Displacement = 40 m east. Average speed = 3 m/s. Average velocity = 2 m/s east.
A car traveling 24 m/s comes to rest in 6 seconds. What is its acceleration?
-4 m/s².
Two students push a box in opposite directions. One pushes with 45 N to the right and the other pushes with 30 N to the left. What is the net force, and what will happen to the box?
Net force = 15 N right. The box will accelerate to the right.
A passenger continues moving forward when a car suddenly stops. Which Newton’s Law explains this, and why?
Newton’s First Law. The passenger’s inertia causes their body to continue moving forward until another force acts on them.
A 0.5 kg football moving at 12 m/s is caught and brought to rest. What is the magnitude of its change in momentum?
6 kg·m/s.
A runner travels 100 m east in 20 seconds, then 60 m west in 10 seconds. Find the total distance, displacement, average speed, and average velocity.
Distance = 160 m. Displacement = 40 m east. Average speed = 5.33 m/s. Average velocity = 1.33 m/s east.
An object’s velocity changes from 5 m/s to 25 m/s in 4 seconds. It then travels at a constant 25 m/s for another 4 seconds. What is its acceleration during each interval?
First interval = 5 m/s². Second interval = 0 m/s².
A box moves across the floor at a constant velocity while someone pushes it with 40 N to the right. What must the friction force and net force be?
Friction = 40 N left. Net force = 0 N because the box has constant velocity.
A 5 kg cart is pushed with 20 N to the right while friction pushes with 5 N to the left. Find the net force and acceleration, then identify the Newton’s Law used.
Net force = 15 N right. Acceleration = 3 m/s² right. Newton’s Second Law.
Two receivers catch identical footballs with the same change in momentum. Receiver A stops the football in 0.05 s. Receiver B stops it in 0.20 s. Which receiver experiences the greater average force, and how many times greater is it? Explain why.
Receiver A experiences 4 times greater average force. Both catches have the same change in momentum and therefore the same impulse, but Receiver A stops the ball in one-fourth the time. Increasing stopping time decreases average force.