3.2 Forces In Motion

Question 1

What is a resultant force?

Answer 1

A resultant force is a single force which has the same effect as the sum of all of the forces acting on the body

Question 2

Define a Newton

Answer 2

One Newton is the force that causes a mass of 1kg to have an acceleration of one metre per second squared

Question 3

What is the equation for weight?

Answer 3

W=mg

Question 4

What are the four forces of nature?

Answer 4

The gravitational force
The electromagnetic force
The weak interaction
The strong interaction

Question 5

What is the equation for tension

Answer 5

T=mg

T-mg=ma

Question 6

What is the normal contact force or reaction force?

Answer 6

It is the force which acts perpendicular to the point of contact of a body and the surface with which it is in contact

Question 7

What is up thrust

Answer 7

Up thrust is the upwards force that a liquid or gas exerts in a body floating in it due to the water displaced

Question 8

A free body diagram must contain

Answer 8

The body on which the forces act
The direction of application of each force
The type of each force
The size of each force

Question 9

What is terminal velocity?

Answer 9

The drag on an object increases as the object accelerates, eventually the drags upwards becomes equal to the weight of the falling object downwards, meaning the resultant force is 0

Question 10

Define equilibrium

Answer 10

If the resultant force acting on an object is 0 then the object is in equilibrium

Question 11

Define the moment of a force

Answer 11

The Moment of a force is the product of a force and the perpendicular distance of its line of action from the point or axis

Question 12

What is the equation for turning moment

Answer 12

Turning moment= magnitude of force (n) x perpendicular distance of force from a fixed point (m)

Question 13

What is the equation for moment

Answer 13

Moment = F x D

Question 14

What is the principal of moments?

Answer 14

The principal of moments states that for an object to be in rotational equilibrium, the sum of the clockwise moments must equal the sum of the anti-clockwise moments

Question 15

Why is torque caused?

Answer 15

The turning motion torque due to a couple is the product of one of the forces and the perpendicular distance between them. He units are Nm

Question 16

Define the centre of mass

Answer 16

The centre of mass of an object is the single point at which all of the mass of an object can be assumed to be situated. For a symmetrical body of constant density this will be at the centre of the object

Question 17

Define the centre of gravity

Answer 17

The centre of gravity of an object is the single point brogue which the entire weight of the object can be thought to act.

Question 18

What is the equation for density

Answer 18

Density p=m/v

Density=mass/volume

Question 19

Define density

Answer 19

Density is defined as mass per unit volume

Question 20

What is Archimedes principle

Answer 20

Archimedes principle states that the up thrust exerted on an object immersed in fluid whether fully or partially submerged is equal to the weight of the fluid that it displaces

Question 21

What is the equation for pressure

Answer 21

Pressure= force/area

P=f/a

Question 22

Define pressure

Answer 22

Pressure is defined as force per unit area

Question 23

What is the equation for up thrust

Answer 23

Up thrust = weight downwards = mg
Up thrust =AHpg ( pressure x area of bottom of ship)
P= density of sea water= 1030kgm-^3
H= distance from the bottom of the ship to the surface