Unit 4 Science Revision

:hysics + The universe

What are three ways that we currently explore the universe?

1. Orbiters and space probes 

2. Probes and landers 

3. Telescopes

Provide two examples of Telescopes currently in use 

• James Webb Telescope 

• Hubble Telescope

Provide two examples of Probes and Landers 

• Perseverance Rover 

• Huygens Probe

Provide two examples of Orbiters and Space Probes 

• New Horizons 

• Europa Clipper

Define a force

A force is a push, pull or twist acting upon an object as a result of its interaction with another object.

Define mass and state the unit of measurement

Mass is the amount of matter in an object and is measured in grams

Define weight and state the unit of measurement 

Weight is a measure of the force of gravity on an object and measured in Newtons

An unbalanced force can cause an object to:

1. Accelerate (speed up)

2. Decelerate (slow down)

3. Start moving

4. Stop moving

5. Change shape

6. Change direction

What is a Balanced force?

Balanced forces are equal in size and act in opposite directions, resulting in no change to an object's state of motion. It remains at rest or moves at a constant speed. Since the forces cancel each other out, the net force on the object is 0.

What are unbalanced forces?

Unbalanced forces are not equal in size, so they don’t cancel each other out. This causes the object to speed up, slow down, or change direction because the net force is not 0.

Define an Applied force

An applied force is a force that is applied to an object by a person or another object

Define a Normal force

A normal force is the force exerted upon an object that is in contact with another stable object

Define Gravitational force

Gravitational force is the force of attraction between any two objects with mass

Define Air resistance

Air resistance is the force that opposes objects motion as they travel through air.

What is Friction

Friction is the force exerted by a surface as an object moves across it.

Define Newtons first law

Newton's first law of motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will remain in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This means that objects resist changes to their state of motion. 

Provide 3 examples of Newton’s 1st law in action.

1. A book lying on a table remains at rest unless someone pushes it, picks it up, or some other force acts upon it. 

2. A hockey puck sliding on ice will continue moving in a straight line at a constant speed until friction from the ice or another force (like a hockey stick) acts upon it. 

3. When a car is moving at a constant speed and suddenly brakes, passengers tend to keep moving forward due to inertia, which is why seatbelts are important. 

Define Newtons second law

Newton's second law of motion defines force as the rate of change of momentum over time, or more simply, F = ma, where F is the net force, m is the mass of the object, and a is its acceleration. This means a larger net force applied to an object causes a greater acceleration, and more massive objects require more force to accelerate to the same extent. 

Provide 3 examples of Newton’s 2nd law in action.

1. Kicking a soccer ball (more force means more acceleration)

2. Pushing a shopping cart (more mass requires more force to achieve the same acceleration)

3. and a car accelerating (more engine force leads to greater acceleration

Define Newtons third law

Newton's Third Law, also known as the law of action and reaction, states that for every action force, there is an equal and opposite reaction force. This means that when one object exerts a force on another object (the action), the second object simultaneously exerts a force of equal magnitude but in the opposite direction on the first object (the reaction). 

Provide three examples of Newtons third law

1. When you walk, your foot pushes backward against the ground (action force). In response, the ground exerts an equal and opposite force forward on your foot, propelling you forward (reaction force). 

2. When a gun is fired, the expanding gases from the gunpowder exert a force on the bullet, pushing it forward (action force). Simultaneously, the bullet exerts an equal and opposite force on the gun, causing it to recoil (reaction force). 

3. A swimmer pushes water backward with their arms and legs (action force). The water, in turn, exerts an equal and opposite force on the swimmer, propelling them forward (reaction force). 

Define Scalar quantities

Scalar quanties are physical quantities that can be completely described by its magnitude (size) alone, without any need for direction.

Define Vector quantities

Vector quantities are physical quantities that have both magnitude (size) and direction.

Give 4 examples of scalar quantities:

• mass

• distance

• speed

• temperature

Give 4 examples of vector quantities:

• displacement

• velocity

• acceleration

• force

Define distance

Distance is a scalar quantity that measures how far an object travels during its motion, expressed in metres (m).

Define displacement

Displacement is a vector quantity that describes how far and in what direction an object is from its starting position, measured in meters.

Describe a motion that has a positive distance and zero displacement.

Walking around a park once until you reach your starting point.

Define speed

Speed is a scalar quantity that measures how fast an object is travelling, calculated as the change in distance over time and expressed in metres per second (m/s).

Define velocity

Velocity is a vector quantity that measures how fast an object is travelling in a given direction, calculated as the change in displacement over time and expressed in metres per second (m/s) with direction.

What is the formula for speed

v (speed) = d (distance) / t (time)

What is the formula for velocity

v (velocity) = s (displacement) / t (time)