Mechanics

Question 1

The equation to find the weight of an object

Answer 1

W = mg

Question 2

Definition of g

Answer 2

g is acceleration due to gravity. Force per unit mass

Question 3

List the SI base units

Answer 3

Candela - Luminosity
KG - mass
Moles - amount of substance
Amp - current
Kelvin - temperature
Second - time
Metre - length

Question 4

What’s the difference between a scalar and a vector

Answer 4

A scalar only has magnitude, a vector has magnitude and direction

Question 5

What’s the gradient of a displacement-time graph

Answer 5

Velocity

Question 6

What’s the gradient of a velocity-time graph

Answer 6

Acceleration

Question 7

What’s the area under a velocity-time graph

Answer 7

Displacement

Question 8

Terminal velocity model answer

Answer 8

As skydiver speeds up, air resistance will increase
Net force on skydiver will decrease, reducing acceleration

Parachute greatly increases the size of the air resistance
When air resistance = weight of skydiver, skydiver is in equilibrium

Question 9

What do free body diagrams show?

Answer 9

All the forces acting on an object

Question 10

Derive the base units for force

Answer 10

F = ma [m] = kg [a] =ms^-1 => [F] = kgms^-1

Question 11

How do you resolve a vector?

Answer 11

Split it into its x and y components using sine and cosine

Question 12

State Newton’s second law and the two equations for it?

Answer 12

The rate of change of momentum of a body is directly proportional to the external resulting force acting upon it. The change of momentum takes place in the direction of that force. F = ma = p/t

Question 13

How do you add two vectors?

Answer 13

Split into components then add components then use Pythagoras to combine components

Question 14

State Newton’s 3rd Law

Answer 14

If object A exerts a force on object B then object B exerts an equal but opposite force back on A

Question 15

What are the criteria for Newton’s Third Law pairs?

Answer 15

Same type of force, same magnitude, opposite direction

Question 16

List the SUVAT equations

Answer 16

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

Question 17

How do you add vectors by scale drawing?

Answer 17

Draw vectors originating from the same point, draw in parallel sides then join corners

Question 18

How do you solve a projectiles question?

Answer 18

Resolve velocity vector, find time to taken to reach apogee using a = -g, double time to find total time,

Question 19

Give the equation for momentum

Answer 19

p = mv

Question 20

State the law of conservation of momentum

Answer 20

Momentum before a collision in a direction is equal to the momentum after a collision

Question 21

Give the equation for Kinetic Energy

Answer 21

E = 1/2mv^2

Question 22

Give the equation for Gravitation Potential Energy

Answer 22

E = mgh

Question 23

State the law of conservation of energy

Answer 23

Energy can neither be created or destroyed therefore it is possible to use mgh = 1/2mv^2

Question 24

Define Centre of Gravity

Answer 24

from the point from the which the weight would act if the object was considered as a particle

Question 25

State the principle of moments

Answer 25

If the total clockwise moment is equal to the total anticlockwise moment and the resultant force is 0 then the object is in equilibrium

Question 26

Equation for moments

Answer 26

M = Fd where d is the perpendicular distance

Question 27

Equation for efficiency

Answer 27

Energy out/Energy in or Power in/Power out

Question 28

Give the formula for work done

Answer 28

W = Fdcos x