Unit 2 Section 1 Mechanics

Question 0

What is the difference between a scalar and a vector?

Answer 0

A vector has magnitude and direction while a scalar only has the former.

Question 1

Is force scalar or vector?

Answer 1

Vector.

Question 2

What are the 3 rules for bearings?

Answer 2

Start from north.
Go clockwise.
Have 3 figures.

Question 3

What is free fall?

Answer 3

The motion of an abject going at an acceleration of g.

The weight is the only force acting on it.

Question 4

What is a projectile?

Answer 4

Any object give an initial velocity and then left to move freely under the influence of gravity.

Question 5

What does a curve on a velocity time graph mean?

Answer 5

The acceleration is changing.

Question 6

What is inertia?

Answer 6

The resistance an object has to a change to its state of motion, including direction and speed.

Question 7

What affects inertia?

Answer 7

The larger the mass, the greater the inertia.

Question 8

What is weight?

Answer 8

It is the force experienced by a mass due to the gravitational field strength.

Question 9

What is weight measured in?

Answer 9

Newtons.

Question 10

How is weight found?

Answer 10

Mass X gravitational field strength.

Question 11

What is the density equation?

Answer 11

Mass = density X volume.

Question 12

Define centre of gravity.

Answer 12

The single point that the whole weight of the object can be considered to act through.

Question 13

What is the critical angle of an object?

Answer 13

It is when the centre of mass is on the edge of the base area. The object will be balancing on its edge.

Question 14

What do free body force diagrams show?

Answer 14

All the forces the world puts on an object, but not the forces the object puts on the world.

Question 15

What is resolving a force?

Answer 15

Splitting up a force into different forces so the calculations are easier to work with.

Question 16

What is a moment?

Answer 16

The turning affect of a force.

Question 17

What is the principle of moments?

Answer 17

For a body to be in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point.

Question 18

What is a couple?

Answer 18

A pair of forces of equal size which act parallel to each other but in opposite directions.
They don’t produce any resultant linear force but do produce a turning force (or torque)

Question 19

What is the formula for finding a torque in a couple?

Answer 19

Torque(Nm) = size of one of the forces(N) X perpendicular distance between the forces (M)

Question 20

What is Newton’s first law?

Answer 20

The velocity if a object wouldn’t change unless a resultant force acts on it.

Question 21

What is Newton’s third law?

Answer 21

For every action there is an equal and opposite reaction.

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

Question 22

A book is put on a table. Explain the forces using newton’s laws.

Answer 22

It is not the third law as gravity pulls down on the books and the table pushes up on the books. These are 2 different sets of forces meaning it isn’t an example of the third law.
The forces are equal and opposite meaning nothing moves so it shows the first law.

Question 23

What are the 2 types of friction?

Answer 23

Contact friction. Between solid surfaces.

Fluid friction.(drag or air resistance)

Question 24

What affects the force of fluid resistance or drag?

Answer 24

The viscosity of the fluid.
It increases as speed increases.(normally directly proportional)
The shape of the object. The larger the area, the greater the resistance.

Question 25

In which direction do frictional forces always act?

Answer 25

The opposite direction to the motion of the object.
They never cause things to move on their own.
They convert kinetic energy to heat.

Question 26

What does terminal velocity look like on an acceleration time graph?

Answer 26

The acceleration falls to zero.

Question 27

Define work?

Answer 27

The amount of energy transferred from one form to another when a force causes a movment.

Question 28

What is the equation for work?

Answer 28

Work (J)= force(N)X distance(M)

Question 29

Define 1 joule.

Answer 29

One joule is the work done when a force of 1 newton moves an object through a distance of 1 metre.

Question 30

What are the equations to find power?

Answer 30

Power (W) = work done(J)
Time(s)
Power= force X velocity

Question 31

What is the centre of mass?

Answer 31

The point at which all of the mass of an object appears to be.

Question 32

When is an object stable?

Answer 32

It is stable when the action of the weight acts though the base.

Question 33

A 650 kg car goes from 100 m/s to rest in 4 seconds. Find the magnitude of the braking force in newtons.
Find it in terms of G.

Answer 33

Acceleration =-25 m/s
650 X 25 = 16250 newtons of force.
16250 ÷ 650 ÷ 9.81 = 2.55 G

Question 34

When is something in equilibrium ?

Answer 34

Sum of clockwise moments = sum of anticlockwise moments.

Question 35

What is mechanical power?

Answer 35

The rate at which energy is transfered.

Question 36

Define a moment.

Answer 36

The moment of a force about a point is equal to the force multiplied by the perpendicular distance between the line of action and the pivot.

Question 37

Define velocity

Answer 37

The rate of change of displacement.

Question 38

Define speed.

Answer 38

The rate of change of distance.

Question 39

Define acceleration.

Answer 39

The rate of change of velocity.

Question 40

How is acceleration found in terms of g?

Answer 40

Divide by 9.81

Question 41

How is power found?

Answer 41

Force X velocity.

Work ÷ time