Law 1
the tendency of an object to resist changes in its state of motion
inertia
What is newtons second law?
F=ma
for every action their is an equal and opposite reaction
What is the weight of a 2kg box sitting on a shelf?
w=mg
w= (2kg)(9.8m/s2)=19.6N
you sitting in seat
Normal and gravity balanced
Newtons first law states:
An object in motion will stay in motion
an object at rest will stay at rest
unless acted upon by unbalanced force
How do we visualize the external forces acting on a object
Free body diagrams
When you push against the wall, the wall pushes back on you with an equal and opposite force
Why do these forces not cancel out?
the forces are acting on different bodies
you on wall
wall on you
A ball moves rightward with a constant velocity after being kicked with 200N force. What is the net force?
0, constant velocity
a ball is in freefall. neglect air resistance
gravity vector
the study of the cause of motion
dynamics
Newtons second law states that acceleration is __________________proportional to the Net Force
According to newtons second law acceleration is __________________ proportional to the mass
directly
inversely
Give a scenario where N=mg
non accelerating horizontal force
A 6kg block of wood accelerates on the tabletop after an applied force of 150 N, the coefficient of friction between the wood block and tabletop is .3, what is the force of friction?
ff=17.64
a duffle bag being dragged right across the floor, by its strap
force tension to right greater than friction force left
Provide the metric units of:
friction, weight and coefficient of friction
Friction- Newtons
Weight- Newtons
Coefficient of friction- unitless
Explain why a large moose would have a hard time catching you if you zigzagged
INERTIA- the large mass of the moose makes it harder for him to change direction. Acceleration and mass are directly proportional, the larger the mass of the moose the more force needed to accelerate (change direction)
Provide the formula for friction
Friction = coefficient of friction x Normal force
A person weighing 55 kg walks by applying 160 N of force on the ground, while pushing a 10-kg object. If the person accelerates at 2 m/s2 , what is the force of friction experienced by the system consisting of the person and the object?
Ff=30N
a backpack hangs motionless from one shoulder (one strap) on a student
Tension and gravity equal
Label the following forces:
The force that opposes motion-
The sum of all external forces-
pulling force along a connecting medium (rope or cord)-
force that acts perpendicular to the surface-
force that is exerted by one object on one or more other objects-
Friction
Net force
Tension
Normal
Applied
Provide the formula for acceleration using newtons 2nd law
a= Fnet/m
Match each scenario to Newtons Laws:
1. A gun recoils
2. mass directly affects acceleration
3. chair pushes up on you as you sit
4. body moves forward as car stops
5. bowling ball moving in direction it was thrown
1. 3rd
2. 2nd
3. 3rd
4. 1st
5. 1st
Two people push a 2,000-kg car to get it started. An acceleration of at least 5.0 m/s2 is required to start the car. Assuming both people apply the same magnitude force, how much force will each need to apply if friction between the car and the road is 300 N?
4850 N
A skydiver descends with a constant velocity. Consider air resistance.
Force air equal to force gravity