Newtons Laws
Which of Newtons laws explains why you feel pushed back into your seat when a car suddenly accelerates?
Newtons first law - inertia
What force prevents you from sinking into the ground while standing?
Normal Force
If an object is not accelerating what must be true about the forces acting on it?
They must be balanced
Why is it easier to keep pushing a heavy box once it starts moving than to get it moving in the first place?
Static friction is greater than kinetic friction, so it takes more force to start moving than to keep moving
You push on a wall, and it doesn’t move. What force does the wall exert on you?
An equal and opposite force pushing back – Newton’s 3rd Law.
If an object is moving at a constant velocity, what can you say about the forces acting on it?
They are in balance (equilibrium, no acceleration)
If you are pushing against a wall and it doesn't move, are you applying a force?
Yes, but there is no net force.
What happens to an objects acceleration if the net force on it doubles but its mass stays the same?
Acceleration doubles (F=ma)
A heavier object and a lighter object are dropped in air. Which one lands first?
The heavier one, because air resistance has less effect relative to its weight
A bug hits a windshield. Which force is greater: the force of the bug on the car or the car on the bug?
They are equal and opposite – Newton’s 3rd Law.
When a magician pulls a table cloth out from under dishes without moving them Which law explains this?
Newton's First
In an FBD of a book sliding to a stop on a tabletop, what forces should be included?
normal, gravity, and friction
A person stands in an elevator that is accelerating upwards. Is the normal force on them greater than, less than, or equal to their weight?
Greater than, because it must counteract gravity and provide additional upward acceleration
A ball is thrown straight up in the air. What is its acceleration at the very top?
-9.8m/s^2, gravity never stops acting on the ball.
A rocket takes off by pushing exhaust gases downward. Why does it move upward?
The exhaust pushes down, and the rocket experiences an equal and opposite force upward – Newton’s 3rd Law
A truck and a small car crash into each other, which experiences the greater force?
A skydiver reaches terminal velocity. What can you say about the forces acting on them?
Gravity and air resistance are in equal magnitude but opposite direction.
You push a box across a floor at a constant speed. What can you say about the forces acting on it?
The applied force and friction are equal, making net force = 0
A box on a rough surface is given a push and then left alone. Why does it eventually stop?
Friction opposes motion and removes energy.
When jumping off a small boat, why does the boat move backward?
The force you apply to push off also pushes the boat in the opposite direction – Newton’s 3rd Law.
3m/s^2
You pull a sled with a rope at an angle, How does this effect the normal force compared to pulling it horizontally?
Normal force is reduced because part of the applied force is lifting the sled upward.
A car suddenly stops, what happens to an unbuckled passenger?
They continue moving forward due to inertia.
You throw a ball straight up while riding in a moving train. Where does it land?
Back in your hand, assuming the train moves at constant velocity – it has the same horizontal motion as you.
If a person in space throws a heavy wrench forward, what happens to them?
They move backward with equal momentum, but at a slower speed if they have more mass.