Mechanics

Question 1

When is an object in equilibrium?

Answer 1

No resultant force and no turning force (sum of moments is zero)

Question 2

Define moment (including equation)

Answer 2

Moment = force x perpendicular distance from line of action of the force to the axis or point of rotation

Question 3

Moment of a couple?

Answer 3

Moment of a couple =FD

Question 4

When does a falling object reach terminal velocity?

Answer 4

When it’s weight (gravitational pull) is equal to the drag force and it no longer accelerates, it falls at a constant velocity

Question 5

Newton’s First Law?

Answer 5

An object remains at rest/constant velocity unless acted on by a resultant force

Question 6

Newton’s Second Law?
Include equations

Answer 6

Resultant force is proportional to the rate of change of momentum.
F = change in momentum/t
F=ma if m is constant and a is uniform

Question 7

Newton’s Third Law?

Answer 7

Force exerted by A on B is in opposite direction, same type and equal to the force exerted by B on A

Question 8

In an elastic collision, what is conserved?

Answer 8

Momentum is conserved
Kinetic energy is conserved

Question 9

In an inelastic collision, what is conserved?

Answer 9

Momentum is conserved
Kinetic energy is NOT conserved

Question 10

What does the area under a force time graph represent?

Answer 10

The impulse (change in momentum)

Question 11

What does the are under a force displacement graph represent?

Answer 11

Fs, work done or energy transferred

Question 12

In W=Fs, what conditions need to be true for it to hold?

Answer 12

Force must be constant and the displacement must be the distance in the direction of the force.

Question 13

What does Hooke’s Law state?
Equation?

Answer 13

That the extension of a spring is proportional to the force applied provided the limit of proportionality is not exceeded
F=kx

Question 14

What effect does a parallel spring system have on the spring constant?

Answer 14

kt = k1 + k2 + …
The spring constant increases

Question 15

What effect does a series spring system have on the spring constant?

Answer 15

1/kt = 1/k1 + 1/k2 + …
The spring constant decreases

Question 16

What effect does a parallel spring system have on the extension?

Answer 16

Extension decreases

Question 17

What effect does a series spring system have on the extension?

Answer 17

Extension increases

Question 18

What does the gradient of a force extension graph represent for something that obeys Hooke’s Law?

Answer 18

The spring constant

Question 19

Define friction

Answer 19

Force that acts between two surfaces that meet

Question 20

Define air resistance

Answer 20

A drag force experienced when moving through air

Question 21

For circular motion, where is the object accelerating?

Answer 21

Towards the centre

Question 22

In circular motion, ____ is always a tangent to the objects path

Answer 22

In circular motion, velocity is always a tangent to the objects path

Question 23

What are the centripetal acceleration equations?

Answer 23

a = v^2 /r
a = w^2 r

Question 24

What is the difference between angular velocity and angular frequency?
What is the equation?

Answer 24

Angular velocity is a vector and used for circles.
Angular frequency is a scalar and used for SHM and waves.
w=2 pi f

Question 25

In circular motion, how do you work out the force acting towards the centre of the circle?

Answer 25

F= mv^2 /r F=mw^2r

Question 26

In a loop de loop, what will the reaction force be at the top?

Answer 26

R=(mv^2/r)-mg

Question 27

In a loop de loop, what will the reaction force be at the bottom?

Answer 27

R=(mv^2/r)+mg

Question 28

What is amplitude for SHM?

Answer 28

Magnitude of the max displacement (+ve)

Question 29

What is displacement for SHM?

Answer 29

Distance from rest position (+ve or -ve)

Question 30

What is frequency for SHM?

Answer 30

Number of oscillations per unit time

Question 31

What is the period for SHM?

Answer 31

Time for one complete oscillation

Question 32

SHM has: an __ proportional to __ from equilibrium position an a in ____ direction to displacement

Answer 32

SHM has: an ACCELERATION proportional to DISPLACEMENT from equilibrium position an acceleration in OPPOSITE direction to displacement

Question 33

What is the acceleration equation for an object in SHM?

Answer 33

a=- w^2 x

Question 34

What is the displacement equation for an object in SHM?

Answer 34

x=Acos(wx)

Question 35

When is vmax in SHM?

Answer 35

At the equilibrium position vmax =+- wA

Question 36

When is amax in SHM?

Answer 36

At max displacement amax = -w^2 A

Question 37

For a simple pendulum, what is the time period? What does it tell us?

Answer 37

T=2pi sqrt(L/g) Where L is the length of the string. T is independent of x or A

Question 38

For a mass-spring system, what is the time period? What does it tell us?

Answer 38

T=2pi sqrt(m/k) Where k is the spring constant. Bigger k, higher f and smaller T Heavier mass, T increases

Question 39

SHM graphs: x against t is a ___ graph (starting from equilibrium position)

Answer 39

a sin graph

Question 40

SHM graphs: v against t is a ___ graph (starting from equilibrium position)

Answer 40

a cos graph

Question 41

SHM graphs: a against t is a ___ graph (starting from equilibrium position)

Answer 41

a negative sin graph

Question 42

When in equilibrium position, a pendulum has: - max __ - min __

Answer 42

In equilibrium: - max kinetic energy - min potential energy (0)

Question 43

When at max displacement, a pendulum has: - max __ - min __

Answer 43

At max displacement: - max potential energy - min kinetic energy (0)

Question 44

In a vertical mass spring system: When compressed, - Ek is __ - Gpe is __ - Epe is __

Answer 44

In a vertical mass spring system: When compressed, - Ek is 0 - Gpe is max - Epe is min

Question 45

In a vertical mass spring system: When at equilibrium, - Ek is __ - Gpe is __ - Epe is __

Answer 45

In a vertical mass spring system: When at equilibrium, - Ek is max - Gpe is 1/2 max - Epe is 1/2 max

Question 46

In a vertical mass spring system: When most stretched, - Ek is __ - Gpe is __ - Epe is __

Answer 46

In a vertical mass spring system: When most stretched, - Ek is 0 - Gpe is min - Epe is max