Physics - Force and Newtons
What is the wordy definition of Newton’s second law of motion?
The acceleration of an object is directly proportional to the net force ating on the object, is in the direction of the net force and is inversely proportional to the mass of the object.
What’s the basic jist of Newton’s second law of motion?
Acceleration is affected in two ways:
- Increased by more force
- Decreased by more mass
Acceleration is directly proportional to?
The net force ating on the object.
Acceleration is inversely proptional to?
The mass of the object.
What is the simple equation explaining Newton’s second law of motion?
What is the simple word equation explaining Newton’s second law of motion?
What is the symbol formula for the momentum of a paritcle?
What is the word formula for the momentum of a particle?
What equation do you get if you substitute $a = \frac{v - u}{t}$ into Newton’s second law?
In the alternate form of Newton’s second law, $F = \frac{mv - mu}{t}$, what does $mv$ represent?
The final momentum.
In the alternate form of Newton’s second law, $F = \frac{mv - mu}{t}$, what does $mv - mu$ represent?
The change in momentum.
What’s another way of thinking about force using the equation $F = \frac{mv - mu}{t}$?
Force is the rate of change of momentum.
How do airbags reduce the force in a car crash, in terms of force and momentum?
Force is the rate of change of momentum. Air bags increase the amount of time it takes to slow down and therefore change momentum.
Why when proving Newton’s Second Law with a cart and a mass, why is the cart on a slope?
To balance out the force of friction.
What angle should the slope be at when proving Newton’s Second Law with a cart and a mass?
The angle where the cart will move without coming to a stop or accelerating.
What is Newton’s First Law?
An object remains at rest or at a constant velocity unless acted upon by a resultant force.
For constant velocity, what must be true about acceleration?
It is $0ms^{-2}$.
Which of Newton’s Laws is the object remaining at constant velocity law?
Newton’s First Law.
Which of Newton’s Laws is the $F = ma$ law?
Newton’s Second Law.
What are the three attributes of the force that Newton’s Third Law says exists?
- Equal in magnitude
- Opposite in direction
- Of the same type
What is Newton’s Third Law?
When object $A$ exerts a force on object $B$, object $B$ exerts a force on object $A$ that is:
- Equal in magnitude
- Opposite in direction
- Of the same type
Newton’s Third Law governs the interaction between what?
Two objects exerting a force.
Which of Newton’s Laws is the “every force has an equal and opposite force” law?
Newton’s Third Law.
How many bees does it take to lift a 747?
6.6 million.
When an object is resting on a surface, the force of weight is acting downwards. What is the equal and opposite force as per Newton’s Third Law?
The weight of the earth pushing against the object.
When an object is resting on a surface, there is a normal contact force from the ground pushing against the object. What is the equal and opposite force as per Newton’s Third Law?
The normal contact force of the object on the ground.
In terms of Newton’s Third Law, how does walking work?
You push backwards against the ground and the ground pushes you forwards.
In terms of Newton’s Third Law, how does a speedboat work?
A motor pushes water backwards, causing the water to propel the boat forwards.
In terms of Newton’s Third Law, how does a rocket work?
Gas is forced out of the back of the rocket, causing the rocket to be forced upwards.
Which of Newton’s Laws governs the fact that throwing a hammer in space will push you in the opposite direction of the hammer?
Newton’s Third Law.
2020-12-15
What is the limitation of the equation $F = ma$?
It only works for situations with a constant mass.
What’s another way of considering force?
The rate of change of momentum.
What’s the rate of change of momentum version of the force formula?
What type of forces does Newton’s Second Law govern?
The resultant force.
What is the definition of impulse?
The change in momentum.
What is the formula for impulse, in terms of force and time?
What is the formula for impulse, in terms of mass and velocity?
How could you explain impulse?
The amount that a force changes momentum.
What is the area under a force time graph?
Impulse.
There are two different forces, one of which is very small and one of which is very large. How can they have the same impulse?
- The small force acts for a long time
- The large force acts for a short time
2021-01-05
What are the two reasons weight and normal contact force can’t be pairs according to Newton’s Third Law?
- Have to be of the same type
- Have to act on seperate bodies
2021-01-21
How should you actually define Newton’s 2nd Law?
Resultant force is equal to the rate of change of linear momentum.
2022-05-11
What happens to apparent weight (via a scale or a newtonmeter) when moving UP in a lift?
It will increase.
What happens to apparent weight (via a scale or a newtonmeter) when moving DOWN in a lift?
It will decrease.
2022-05-17
What’s a trick when asked to compare the speeds of two objects that move in the same time if you aren’t given their speeds directly?
The distance moved will be proportional to the speed.