Physics 1: Kinematics & Newton

Question 1

Newton’s First Law (Inertia)

Answer 1

An object in motion at constant velocity or at rest will stay that way, unless acted upon by an external force.

Question 2

Newton’s Second Law

Answer 2

F(net) = ma

Question 3

Newton’s Third Law

Answer 3

F(AB) = -F(BA)

Question 4

Force on X

Answer 4

Product of (mass of X) and (acceleration of X) F=ma

Question 5

If you have a POSITIVE net acceleration, he normal force must be ( > or < ) m*g

Answer 5

Greater than (>)

Question 6

Fill in the blank with: ( > ) or ( < )

If you have a NEGATIVE net acceleration, the normal force must be _______ m*g

Answer 6

Less than (<)

Question 7

F(net) =

Answer 7

F(net) = F(N) - mg = m a(net)

Question 8

Air resistance

Answer 8

Function of v^2 and k, where “k” is proportional to the density of air and the surface area of the mass.

Question 9

Kinetic friction

Answer 9

f(k) =u(k)F(n)

Question 10

Static Force: F(s)

Answer 10

F(s) = F(applied)

Question 11

Fs(max)

Answer 11

minimum force required to get object to move = u(s)F(n)

Question 12

Static and kinetic co-efficient relationship

Answer 12

µ_s is ALWAYS > µ_k

Question 13

What forces are acting on a box at rest on an inclined plane

Answer 13

f(s) = f(applied) = mgsin(theta)

Question 14

fs(max)=

Answer 14

u(s)mgcos(theta)

Question 15

As the angle of an inclined plane (θ ) increases, what happens to the

a) applied force,
b) static force f_s
c) MAXIMUM static friction (f_s,max)?

Answer 15

As θ increases,

a) f_applied increases,
b) the static force increases
c) f_s,max DECREASES

Question 16

Gravitational Force

Answer 16

F= (Gm₁m₂)/r²

Two masses will exert an attractive force on one another inversely proportional to the square of the distance between them.

Question 17

Uniform Circular Motion

Answer 17

The net force on an object moving at a constant speed on a circular path points toward the center of the circle.

Question 18

F(centripetal)

Answer 18

F(c)=(mv^2)/r

Question 19

Centripetal Acceleration

Answer 19

a(c) = v^2/2

Question 20

Circumference of a circle

Answer 20

C = 2(pi)r Conversion: 2(pi)rad = 360 degrees

Question 21

Theta of a circle (relation to arc length (s) and radius (r) )

Answer 21

theta= s/r

Question 22

Angular speed (w)

Answer 22

2(pi)f = v/r

Question 23

Torque

Answer 23

rotational analog of force is a vector Units: Newton meter (N*m) NOTE: Joules are (N*m) but scalar Torque= F*l l=(r)(sin(theta))

Question 24

Torque rotational convention

Answer 24

Torque > 0: Counterclockwise Torque < 0: Clockwise

Question 25

Rotational equilibrium

Answer 25

An object is in rotational equilibrium when the sum of the torques acting on it is zero.

Question 26

Work

Answer 26

Work=Fd cos (theta) SCALAR unit: joules “transfer of energy” N*m = Joules

Question 27

“Positive Work”

Answer 27

Work done on a system = transfer of energy INTO system. KE goes up

Question 28

Energy

Answer 28

JOULES Kinetic Energy = (1/2)mv^2

Question 29

Average Power (Watt)

Answer 29

Watt = Joules/second P=change in energy/change in time P= F*v

Question 30

Work Energy Theorum

Answer 30

Work(net) = change in KE +work: gain KE -work: lose KE

Question 31

How much work is done by F(Grav) in a satellite moving in a circular orbit?

Answer 31

Work in a circle: speed isn’t changing W(net) = change in KE = zero [although velocity IS changing bc the direction is changing, the SPEED is not. Speed is scalar)

Question 32

Gravitational Potential Energy

Answer 32

U = mgh = F*d

Question 33

Types of PE

Answer 33

1.Gravitational Potential Energy

2. Elastic Potential Energy
3. Chemical Potential Energy

4.Electrical Potential Energy

5.Nuclear Potential Energy

Question 34

Conservation of Mechanical Energy

Answer 34

When conservative forces act on an object, its total mechanical energy is conserved. Work(cons force) = [(delta) KE - [(delta) PE)]

Question 35

Conservative Forces: i) Is Mechanical energy conserved? ii) Is it path independent? iii) Examples

Answer 35

i) Yes, Mech Energy is conserved ii) Yes, it is path independent iii) Ex: Gravity, Electrostatic, Elastic

Question 36

Non-Conservative Forces: i) Is Mechanical energy conserved? ii) Is it path independent? iii) Examples

Answer 36

i) No, mech energy is NOT conserved ii) NO, it is NOT path independent iii) Ex: friction, drag, pushing+pulling (pressure) (don’t forget energy lost to heat)

Question 37

If you push a rock up a mountain, you raise its gravitational PE, but not its KE. Why does this not violate the Work-Energy Theorum?

Answer 37

Work(net) = Work(person put in) + Work(gravity) But W(person) is a non-conservative source added to the system. W(gravity) is a conservative source. Conservative forces only TRANSFER “funds”. They never make you richer/poorer. (ie: Checking=KE; Savings=PE) W(net) - W(cons) = W(noncons) (delta)KE - (-(delta)PE) = (delta)KE + (delta)PE = W(noncons)

Question 38

Conservation of Linear Momentum

Answer 38

The total momentum of a system of objects is conserved as long as no external forces act on that system. Momentum = p= vector.

Question 39

Inlastic Collision

Answer 39

• When a collision results in production of heat, light, sound, or deformation

As long as no external forces are present:
Conservation of Momentum:

m₁v₁ + m₂v₂ = m₁v₁ +m₂v₂

No Conservation of Kinetic Energy

KE_i > KE_f

because: KE_i = KE_{f +} Energy lost to heat or light

(1/2)m₁v_1i²+ (1/2)m₂v_2i² > (1/2)m₁v_1f² + (1/2)m₂v₂²

Question 40

Completely Elastic Collision

Answer 40

Conservation of Momentum:

m₁v₁ + m₂v₂ = m₁v₁ +m₂v₂

Conservation of Kinetic Energy

KE_i = KE_f

(1/2)m₁v_1i²+ (1/2)m₂v_2i² = (1/2)m₁v_1f² + (1/2)m₂v₂²

Question 41

Inelastic Collision

Answer 41

Conservation of Momentum:

m1v1 + m2v2 = m1va +m2v2

No Conservation of Energy:

KE(initial) = KE(final) + heat and deformation energy

Question 42

Totally inelastic collisions

Answer 42

• objects collide and stick together rather than bouncing off of each other and moving apart

Conservation of Momentum

m₁v_1i + m₂v_2i = (m₁+m₂)v_f

• Energy not Conserved:*
• KE(initial) = KE(final) + heat and deformation energy*

Question 43

Two objects with equal masses are moving toward each other with the same speed. How do they move after the collision if the collision is (i) elastic? (ii) totally inelastic?

Answer 43

i) Velocities maintain same speed but switch directions ii) they stop: m1v1 + m2v2 = (m1 + m2)vf vf = zero. (so they stop)

Question 44

Impulse

Answer 44

A force applied to an object over time causes a change in the object’s momentum called an impulse. I = (delta)p = F(avg)*(delta)t

Question 45

Power

Question 46

Work Energy Theorum

Answer 46

a direct relationship between the work done by all the forces acting on an object and the change in kinetic energy of that object. The net work done on or by an object will result in an equal change in the object’s kinetic energy

Question 47

Efficiency

Question 48

Mechanical Advantage

Question 49

Hanging block by two strings

Question 50

Two pulley system

Question 51

Six pulley system

Question 52

Center of Mass diagram

Question 53

Center of Mass

Question 54

Work, Energy Momentum

Essential Equations