1.2 Forces And Newton’s Laws Flashcards
In physics a ______ is a measurable influence that causes something to move
Force
Newton’s first law?
Any object continues at rest or at constant velocity unless an external force acts on it!
External forces give objects acceleration. The acceleration is proportional to the force applied, and the constant of proportionality is the
Mass (meaning the more mass a force has the more acceleration it will give)
Newtons 2nd Law?
F=ma, The greater the mass of an object the more force it will take to accelerate that object
What is the Si unit of a force
Newton (N)
Any object of mass m falls with an acceleration off (9.81) downward, meaning it must be acted on by a force, this downward force due by the gravitational attraction between earth and the object is called the objects..?
Weight
Direction: down toward the centre of the earth
W=mg, therefore the weight of an object is a force not a mass
A force that only acts on objects at rest is called the
an upward force called the contact force cause objects are in contact like a statue and a table, when a contact force acts perpendicular to the surface we call it the NORMAL FORCE (FN)
Newtons 3rd law?
Forces come in pairs, for every action there is an equal and opposite reaction. For every force applied to a body there is a force applied by that body.
When an object A exerts a force on B and B exerts a force equal in size but inn opposite direction on A this vans be referred to as Newtons ___ law
3rd
The force applied by one body A on another object B is known as the
Action
The second force B responding to the force exerted by Object A is known as the
Reaction
Action and reaction forces act on
Different objects
Not action and reaction forces
Action and reaction forces
List the 4 fundamental forces
- Electromagnetic force
- Gravitational force
- Strong nuclear forces
- Weak nuclear forces
List the 3 derived forces
- Normal force
- Tension force
- Friction force
What force do we see when pulling on a rope
Tension force
There is a ball hanging by a string, gravitational force acting down on it so why doesn’t it fall?
Because of the tension force acting alone the string keeping it up.
Any force that appears as a result of pulling on a rope, a string or anything similar is a
Tension force
Tension forces are opposite to
Normal forces
General info
Instead of resisting compression like normal forces, tension forces resist forces that cause things to stretch. When we hang a ball on a rope the rope applies a force to the ball which makes it resist being stretch out out, the result is tension.
How are tension and normal forces opposite to each other
When an object is not pushing against a surface the Normal force= 0
When an object is not pulling on a rope the Tension force= 0
If a ball hanging from a rope has a mass of 10kg, what is the tension force
98.1 N (up)
- we look at the forces acting on the ball= gravity (downward) and the tension force (pulling upward) being applied by the rope onto the ball.
- we see the ball isn’t moving so the forces must cancel out.
- we have to find force of gravity, Fg
Fg=ma, m=10, a=9.81 m/s^2 (down)
= 98.1 N (down) for the weight of the ball - since the gravitational force must be cancelled by the tension on the rope, Fg=Ft, hence Ft is 98.1 N (up)
The ____ force is directed away from the body/ball along the cord
Tension
The cable in tension forces is assumed to be
Massless and unstretchable
The resistance we get by a bonding between a body we’re trying to push and its surface is known as a
Friction force
The friction force is directed along the surface, _______ to the direction of the intended motion
Opposite
When we see the word (motion) the resistance is ______friction (object is moving)
Kinetic
When we see the word (tends to move) the resistance is ______friction (object at rest while pushing/not moving)
Static
To find static and kinetic friction we use the same rule
F= uN
The coefficient of kinetic friction is always smaller than the static friction, why?
Because static friction is motionless, meaning moire friction = larger coefficient of friction
Is force vector or scalar
Vector
The weight of an object is a force?
True, weight should be measured in Newtons even
The acceleration of a body ______ on the applied force
Depends
In the phrase normal force what does normal mean?
The force exerted by a surface that is PERPENDICULAR to the surface (perpendicular must be in the sentence)
A lizard (mass m) basks in the sun on a sloping rock, the net force is
Zero
What is the force required to accelerate a mass of 10.0 kg at 4.00 m/s^2
F=ma, 10(4) = 40 N
