Mechanics

Question 1

What property does a scalar quantity have?

Answer 1

Magnitude only.

Question 2

What properties do vectors have?

Answer 2

Both magnitude and direction.

Question 3

Examples of vector quantities:

Answer 3

Velocity, displacement, acceleration, forces, momentum, weight, moments.

Question 4

Examples of scalar quantities:

Answer 4

Speed, distance, electrical power, charge, mass, energy, current, potential difference.

Question 5

Speed is…

Answer 5

…rate of change of distance.

Question 6

Velocity is…

Answer 6

…rate of change of displacement.

Question 7

Acceleration is…

Answer 7

…rate of change of velocity.

Question 8

Equation for acceleration using velocities:

Answer 8

a=Δv/Δt

Question 9

What is unit acceleration measured in?

Answer 9

ms^-2

Question 10

The gradient of a velocity time graph represents what?

Answer 10

Acceleration.

Question 11

The area under a velocity time graph represents what?

Answer 11

Displacement.

Question 12

Define a moment.

Answer 12

The turning effect of a force at a distance perpendicular to the force.

Question 13

Equation for moments:

Answer 13

M = Fd

Where:
M is the moment.
F is the force.
d is the distance perpendicular to the force from the pivot.

Question 14

Moments are measured in what?

Answer 14

Nm.

Question 15

Centre of mass is what?

Answer 15

The mean position of the mass of an object.

Question 16

Centre of gravity is what?

Answer 16

The position at which weight acts if the object is considered as a single position; the point at which there is no moment due to weight.

Question 17

In a uniform gravitational field, what can be said about the centre of mass and the centre of gravity?

Answer 17

They are in exactly the same place.

Question 18

An object is stable, when?

Answer 18

If the line of action from the centre of gravity lies within the base of the object.

Question 19

How can an object be made more stable?

Answer 19

An object can be made more stable by lowering the centre of gravity or by widening the base.

Question 20

What is the principle of moments?

Answer 20

A system can be said to be in equilibrium if the sum of the total anticlockwise moments equals the sum of the total clockwise moments.

Question 21

What equipment can be used to find the centre of gravity of an object?

Answer 21

A clampstand.
A plumbline.
A nail.

Question 22

Equation for kinetic energy:

Answer 22

Ek = 1/2 mv^2

Question 23

Equation for gravitational potential energy:

Answer 23

ΔEp = mgΔh

Question 24

Elastic potential energy equations:

Answer 24

Eel = 1/2 Fx
or
Eel = 1/2 kx^2

Question 25

Equation for work done:

Answer 25

W = Fscosϴ

Question 26

What can a vector be resolved into?

Answer 26

A horizontal component and a vertical component.

Question 27

How do we resolve to find horizontal and vertical components of vectors?

Answer 27

Use trigonometry. Sine to find the vertical component. Cosine to find the horizontal component.

Question 28

What does SUVAT stand for?

Answer 28

``` S for displacement/m. U for initial velocity/ms^-1 V for final velocity/ms^-1 A for acceleration/ms^-2 T for time/s ```

Question 29

What are the four equations of motion?

Answer 29

v=u+at s=ut+1/2at^2 v^2=u^2+2as s=1/2(u+v)t

Question 30

When can the equations of motion be used?

Answer 30

If acceleration is constant!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Question 31

How do we calculate the motion of projectiles?

Answer 31

Resolve the given vector into vertical and horizontal components and write out the suvat for each. Work from there to solve the problem.

Question 32

How do you solve parabola problems?

Answer 32

Resolve the vector into vertical and horizontal components then write suvat for each on the first half of the parabola. Don’t forget to do the same to the second half of the parabola because if something goes up it also comes down.

Question 33

State Newton’s 1st Law of Motion.

Answer 33

An object will continue to move with a uniform velocity unless it is acted on by a resultant external force.

Question 34

State Newton’s 2nd Law of Motion.

Answer 34

F=ma Force in Newtons (N). Mass in kilograms (kg). Acceleration in metres per second squared (ms^-2).

Question 35

State Newton’s 3rd Law of Motion.

Answer 35

Every action has an equal and opposite reaction. (If object A exerts a force on a second object, B, then B exerts an equal, but opposite, force back on object A).

Question 36

A magnet exerts a magnetic force on a lump of iron. What is the Newton’s 3rd Law pair of these forces?

Answer 36

The iron exerts a magnetic force on the magnet.

Question 37

What is the Principle of Conservation of Momentum.

Answer 37

The Principle of Conservation of Momentum states that in a closed system momentum is conserved.

Question 38

What is a closed system?

Answer 38

A system where there are no external forces acting.

Question 39

Equation of momentum.

Answer 39

p=mv Momentum in kgms^-1 Mass in kg Velocity in ms^1

Question 40

Is momentum a vector or a scalar?

Answer 40

Vector quantity.

Question 41

Resultant force of an object can be described as rate of change of what (Newton’s 2nd)?

Answer 41

Momentum.

Question 42

Recoil is a result of what?

Answer 42

The Principle of Conservation of Momentum. If objects didn’t recoil then momentum would not be conserved.

Question 43

Static objects are objects that can be said to be in what?

Answer 43

Equilibrium.

Question 44

An object in equilibrium has what resultant force?

Answer 44

0 Newtons.

Question 45

Static objects can be either what or what?

Answer 45

Stationary or have constant velocity (Newton’s 1st Law).

Question 46

First step for calculating forces for statics is...

Answer 46

...ΣF=0

Question 47

If the static is on a slope the angle between the slope and the horizontal is the same as what?

Answer 47

The angle at the top of the resolved vector.

Question 48

Dynamics are what?

Answer 48

Situations involving resultant forces and accelerations.

Question 49

First step for dynamics questions...

Answer 49

...ΣF=ma