Forces

Question 1

Define the term force and give its units

Answer 1

Force - a push or pull that alters, or tends to alter, the state of motion of a body - measured in Newtons (N)

10N ~1kg

Question 2

How can forces effect an object?

Answer 2

• Force changes the state of motion of an object
• Force causes acceleration, deceleration or a change in direction, the more force the greater the acceleration or deceleration
• Force changes the shape of the object

Question 3

What are newtons three laws?

Answer 3

1. Law of inertia
2. Law of acceleration
3. Law of reaction

Question 4

Describe Newtons first law of inertia

Check text book

Answer 4

• An object will continue in a state of rest or uniform motion/velocity unless acted upon by an external force

• If an unbalenced force acts on an object, it will accelerate in the direction of the unbalenced force
• If an object is given an intial velocity and there are no unbalanced forces action on it, it will remain in a state of uniform motion

Question 5

Describe Newtons second law of acceleration

Answer 5

• When a force acts on an object, the object is accelerated by an amount directly proportional to the force applied and inversly proportional to the mass of the object
• F = ma Force = mass x acceleration

Question 6

Describe Newtons third law of reaction

Check text book

Answer 6

• For every action force there is an equal and oppostie reaction force

Question 7

Give the equation for force

Answer 7

Force = mass x acceleration

F = ma

Units: N

F = force
m = mass
a = acceleration

Question 8

Define net force

Answer 8

Net force - the balence of vertical forces pushing a body up and down, and horizontal forces pulling back and forward

• If net force is zero the there is no change in movement, all forces are balenced
• If net force is either positve or negative then movement will occur, the forces are unbalenced

Question 9

Name 4 types of force

Answer 9

Types of force:
* Weight
* Reaction force
* Friction
* Air resistance/ fluid friction

Question 10

Define weight

Answer 10

Weight - gravitaional pull exerted through the bodies COM towards earth

Question 11

Give the equation for weight

Answer 11

Weight = mass x gravitaional acceleration

w = mg

Units: N

w = weight
m = mass
g = gravitational acceleration

Question 12

Define reaction force

Answer 12

Reaction force - equal and opposite force exerted in response to the action force

Question 13

Define friction

Answer 13

Friction - the force that opposes the motion of two surfaces in contact

Question 14

Name four factors that affect friction

Answer 14

1. Roughness of the grounds surface, rougher = more friction, e.g rubber running track
2. Roughness of the contact surface, rougher = more friction, e.g. track spikes
3. Temperature, hotter = more friction, e.g. F1 tires
4. Size of the normal reaction, NL 3

Question 15

Define air resistance

Answer 15

Air resistance - opposes motion of a body travelling through air