Forces And Motion

Question 1

What is the unit of moments

Answer 1

Nm (Newton metres)

Question 2

Why is it easier to undo a nut with a long spanner?

Answer 2

There is more leverage, allowing a much greater turning force to be exerted

Question 3

What is the principle of moments?

Answer 3

For an object in equilibrium, the sum of the anti-clockwise moments about any point is equal to the sum of clockwise moments about that point

Question 4

How do you increase stability?

Answer 4

Making its base as wide as possible

Making its centre of mass as low as possible

Question 5

Why will an object topple?

Answer 5

If the line of action of its weight is outside its base. (Resultant moment)

Question 6

What do levers have?

Answer 6

A pivot, a force pushing at one end and a load being lifted

Question 7

What can the distance from the pivot change about a lever?

Answer 7

It can become a force multiplier

Question 8

What is Hooke’s law?

Answer 8

The extension is proportional to the force

The spring will go back to its original length when the force is removed

Question 9

How do you see the elastic limit from a graph?

Answer 9

When the graph line starts to curve

Question 10

What is an elastic material?

Answer 10

One that will return to its original shape when the force applied to it is taken away

Question 11

What is a plastic/Inelastic material?

Answer 11

One that stays deformed after you have taken the force away

Question 12

What is the equation for Hooke’s law?

Answer 12

F = k x X
F- applied force (N)
K- spring constant (N/m or N/cm)
X- the extension (m)

Question 13

What is the equation for moments?

Answer 13

Moment = force x perpendicular distance from the pivot to the line of action of the force

Question 14

What is the centre of gravity?

Answer 14

The point where the weight of an object acts

Question 15

How do you work out the energy need to lift an object a height?

Answer 15

M x g x h

Question 16

What keeps planets in orbit?

Answer 16

Gravity

Question 17

What is the gravitational field strength on earth?

Answer 17

9.8N/kg (can be rounded to 10)

Question 18

How do you work out the orbital speed?

Answer 18

2π x orbital radius / time period

Question 19

Where is the asteroid belt?

Answer 19

Between Mars and Jupiter

Question 20

What is the orbit of a comet?

Answer 20

A flat elliptical orbit, at some points it is very near the sun and at others it is very far away

Question 21

Why do comets move faster at some points in their orbit?

Answer 21

Some points in their orbits mean they are closer to the sun and the gravitational pull increases.

Question 22

What is terminal velocity?

Answer 22

The constant velocity reached when drag force = the force of gravity

Question 23

What is the equation for resultant force?

Answer 23

Resultant force = mass x acceleration (ma)