Newton's Third Law
A hammer strikes a nail. Draw the free body diagram with all forces included.
A skateboarder pushes off a wall and starts moving. What type of force caused this motion?
An unbalanced force; the push from the wall accelerates the skateboarder.
If a toy car doubles its speed, what happens to its kinetic energy?
Kinetic energy increases by 4 times.
Dropping a raw egg from a table versus a chair: which hits with more force?
The egg from the chair hits with more force due to higher speed.
In a ramp experiment, if the slope is kept constant, what can change in each trial?
When you jump off a small boat onto a dock, why does the boat move backward?
Because your push on the boat the boat pushes back. Equal and opposite in direction.
Two people are tugging on a rope with equal force in opposite directions. What happens to the rope?
The rope doesn’t move because the forces are balanced.
A bowling ball and a tennis ball roll at the same speed. Which has more kinetic energy? Why?
The bowling ball. More mass → more kinetic energy at the same speed.
How does wrapping an egg in bubble wrap help it survive a fall?
The wrap spreads out the force over a longer time, reducing impact.
How could you measure how fast a marble rolls down a ramp?
Use a stopwatch for time and a ruler for distance.
A football player collides with another player. How does Newton’s Third Law explain the forces felt by each?
Both players experience forces that are equal in strength and opposite in direction.
A sled slides faster when more people push on it. Why?
The sled slides faster when more people push because the total force on the sled is greater. If the force increases and the mass stays the same, the sled accelerates more, so it moves faster.
A skateboarder goes down a hill and then speeds up. What happens to kinetic energy?
Kinetic energy increases as speed increases.
What design feature could slow down an egg without adding mass?
A parachute or air resistance device.
A student measures how far a marble rolls down different ramps. What is the dependent variable?
The distance the marble rolls.
Two cars are pushed with the same force, but one is heavier. Which moves faster? Why?
The lighter car moves faster. Heavier car moves slower.
A toy car is rolling down a ramp. If the ramp surface is changed from smooth to rough, what happens to the car’s motion and why?
The car slows down because friction opposes motion, reducing speed
A toy car rolls down two ramps of different heights but ends at the same flat surface. Which ramp gives the car more kinetic energy at the bottom, and why?
The taller ramp gives more kinetic energy because the car gains more speed from a greater drop (more potential energy converted to kinetic energy).
If two eggs are dropped from the same height, but one is wrapped in bubble wrap and the other isn’t, how does Newton’s Third Law explain the difference in their impact?
Both eggs exert the same force on the ground, but the bubble wrap spreads and absorbs the force, so the egg is less damaged.
A student is testing cars with different weights on a ramp. What are three ways they can make their experiment more accurate, and why would these help?
repeat several times; keep ramp the same (angle, surface, starting position); use precise tools (ruler or stopwatch)
A skateboarder pushes backward on a wall with a force of 150 N while trying to launch off a ramp. Identify 2 factors could change the skateboarder’s speed.
mass, friction, ramp angle, air resistance.
Two people push a heavy box together. How can they increase the box’s acceleration without changing the mass?
By increasing the total applied force. (Adding more people/pushing with more force)
A ball rolls down a hill and hits a stationary can. How would doubling the ball’s speed affect the distance the can moves?
Doubling the speed quadruples the kinetic energy, likely causing the can to move much farther.
Design a modification that could prevent an egg from breaking when dropped from 5 feet. Explain using forces, speed, and energy concepts.
Possible answer: Use straws or foam to absorb force, add a parachute to reduce velocity, or a combination. This reduces acceleration and kinetic energy upon impact.
You want to test how the surface type (smooth, rough, or carpeted) affects how far a toy car rolls when given the same push. Describe how you would design this experiment, including your independent variable and dependent variable.
Independent variable: Surface type (smooth, rough, carpeted) – this is what you are changing.
Dependent variable: Distance the toy car rolls – this is what you are measuring.