Forces in Action
What is a force?
A push or pull on an object.
What causes objects to change speed in a crash?
Forces
What is friction?
A force that opposes motion between two surfaces.
What happens to an object’s speed if a force is applied in the same direction as its motion?
it speeds up!
Which of Newton’s laws explains why you feel pushed backward when a car suddenly accelerates?
Newton’s First Law
What is the relationship between mass and acceleration if force stays constant? Direct or inverse?
As mass increases, acceleration decreases. (inverse)
True or False: Larger objects always experience greater forces in collisions.
False, they experience the same force
Name a situation where friction helps motion.
Walking, brakes stopping a car, etc.
What happens to an object’s speed if a force is applied in the opposite direction?
It slows down
Which of Newton’s laws states that F = ma?
Newton’s Second Law.
If an object is not moving, what does this say about the forces acting on it?
The forces are balanced.
Two skaters push off each other. One skater is twice as massive as the other. How do their accelerations compare?
The smaller skater accelerates twice as much.
Why do ice skates slide more easily on ice than on grass?
Ice has less friction than grass.
Why would a soccer ball eventually stop rolling across the field after kicked?
Friction slows it down.
Which law explains why a rocket moves forward when it expels gas backward?
Newton’s Third Law.
True or False: All forces cause motion.
False, forces can balance each other out.
Why do both objects in a collision experience the same amount of force?
Newton's Third Law—forces come in pairs.
What type of surface creates the most friction: smooth or rough?
rough
What is acceleration?
The rate at which an object’s velocity changes.
A hockey puck slides across the ice and eventually stops. Which law explains why it stopped?
Newton’s First Law, with friction as the unbalanced force
A ball is rolling down a hill. Name two forces acting on it.
Gravity and friction
A shopping cart doubles its mass. How does this affect the force it exerts when it collides with another object?
The force doubles
An object doubles in mass. How does this affect the force needed to achieve the same acceleration?
The force also doubles.
If force is doubled and mass stays the same, how does acceleration change?
acceleration doubles
An object is pushed with a force of 20 N and has a mass of 5 kg. What is its acceleration?
4 m/s²