Forces In Action

Question 1

Define a force

Answer 1

A force of 1 Newton will give a 1kg mass an acceleration of 1ms⁻² in the direction of the force.

Question 2

What is weight?

Answer 2

The gravitational force on an object, measured in Newtons.

Question 3

What is mass

Answer 3

Amount of matter, a base quantity measured in kilograms.

Question 4

How can you determine weight?

Answer 4

Using a newtonmeter

Question 5

What is the centre of mass?

Answer 5

The centre of mass of an object is an imaginary point where the entire weight of an object appears at act.

Question 6

Define centre of ass

Answer 6

A point through which any externally applied force produces straight line motion but no rotation

Question 7

Determining the centre of gravity:

Answer 7

Make small holes along the edge of the objects made of card.

Insert a pin through one of the holes and hold the pin firmly in a clamp.

Hang a plumb-line from the pin and draw a line along the vertical string of the plumb-line.

Repeat the process for the other holes and the point of intersection is the centre of gravity and centre of mass.

Question 8

What is drag

Answer 8

A frictional force that opposes the motion of an objects

Question 9

How does cross- sectional area affect the magnitude of a drag force?

Answer 9

The larger the cross-sectional area results in a greater drag

Question 10

What is the relationship between drag force and speed?

Answer 10

Drag force is directly proportional to speed²

Question 11

At the first instant an object starts to fall, what is drag force equal too?

Answer 11

No drag force, the total force is equal to the weight.

Question 12

As the object falls, its speed increases and what happened to the drag?

Answer 12

The magnitude of drag also increases.
Therefore, net force= mg-D
a =(mg-D)/m

Question 13

When the object reaches terminal velocity what is the drag force?

Answer 13

The drag force is equal and opposite to the weight.

The object has zero accelerate and speed is constant

Question 14

Define a moment.

Answer 14

Force times the perpendicular distance of the line of action of force from the axis or point of rotation.

Question 15

What are the units for moments?

Answer 15

Nm

Question 16

For a body to be in equilibrium, what conditions are required?

Answer 16

Net force=0
Net moment=0

Question 17

Define principle of moments.

Answer 17

For a body in rotational equilibrium, the sum of clockwise moments is equal to the sum of anticlockwise moments.

Question 18

Define the torque of a couple

Answer 18

One of the forces x the perpendicular separation between the forces .

Question 19

Equation of torque

Answer 19

T= Fd

Question 20

Define density.

Answer 20

Mass per unit volume

Question 21

Determine density

Answer 21

Mass can be measured using a digital balance.

For liquids, you can use measuring cylinder to determine the volume.

For irregular solids,add water to a measuring cylinder and then add the object and measure the difference in volume.

Question 22

How to find the pressure exerted by any vertical liquid?

Answer 22

P= hdg

h= height of the liquid column
d= density of the liquid
g= gravity

Question 23

Define Archimedes’ principle.

Answer 23

The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.

Question 24

What is the density of water?

Answer 24

1000kgm-3

Question 25

Finding the normal force on an inclined plane.

Answer 25

F(N) = mgcos (theta)

Question 26

Factors affecting the drag on an object?

Answer 26

Speed of object
Shape of object
Roughness/ texture of object
Density of the fluid the object is travelling in