Physics KS3 Forces (January 2023) (in order) Flashcards
- What is a force?
A force is a push or pull that acts on an object
- Forces are measured in ……. (units)
Newtons or N / (N must be uppercase)
- To measure a force the instrument you use is a …….
newtonmeter or forcemeter or spring balance
- Sometimes the two bodies must be touching for the force to be present these are called ……. forces.
Contact
- Sometimes one body can have an effect on another without having to be in contact, these forces are known as ……. forces.
Non-contact
- Description: Forward push of an object moving on a solid surface – Name the force and state whether contact or non-contact
Thrust/Forward force – Contact
- Description: Attraction (pull towards) or repulsion (push away) of magnets and magnetic materials – Name the force and state whether contact or non-contact
Magnetism/Magnetic – Non-contact
- Description: Attraction between two objects with mass (Gravity) – Name the force and state whether contact or non-contact
Weight – Non-contact
- Description: Upward push of water on an object – Name the force and state whether contact or non-contact
Upthrust – Contact
- Description: Upward push of a solid surface on an object – Name the force and state whether contact or non-contact
Normal contact – Contact
- Description: Force which slows objects moving along a solid surface – Name the force and state whether contact or non-contact
Friction – Contact
- Description: Force which slows objects moving through water – Name the force and state whether contact or non-contact
Water resistance/drag – Contact
- Description: Force which slows objects moving through air – Name the force and state whether contact or non-contact
Air resistance/drag – Contact
- Description: The force pushing up on an object as it moves through the air, caused by differences in air pressure. – Name the force and state whether contact or non-contact
Lift – Contact
- Description: Forces caused when objects eg springs, string are stretched/compressed – Name the force and state whether contact or non-contact
Tension/Compression – Contact
- A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. This single force is called the ……………… force.
resultant
- What is the resultant force when the forces on an object are balanced?
Zero or 0 N
- State the effect of unbalanced forces on a moving object if the resultant force direction is in the direction that the object is moving. Which one of the following is true? 1) It will stay stationary 2) It will keep moving at a constant speed 3) It will speed up 4) It will slow down
3) It will speed up
- State the effect of balanced forces (zero resultant) on a moving object. Which one of the following is true? 1) It will stay stationary 2) It will keep moving at a constant speed 3) It will speed up 4) It will slow down
2) It will keep moving at a constant speed
- State the effect of balanced forces (zero resultant) on a stationary (not moving) object. Which one of the following is true? 1) It will stay stationary 2) It will keep moving at a constant speed 3) It will speed up 4) It will slow down
1) It will stay stationary
- State the effect of unbalanced forces on a stationary (not moving) object. Which of the following is true? 1) It will stay stationary 2) It will keep moving at a constant speed 3) It will speed up 4) It will slow down
3) It will speed up
- State the effect (if any) of unbalanced forces on a moving object if the resultant force is in the opposite direction to the direction of the moving object. Which one of the following is true? 1) It will stay stationary 2) It will keep moving at a constant speed 3) It will speed up 4) It will slow down
4) It will slow down
- How can friction between solid objects be reduced?
Lubrication eg oil on bike chains or wax on snowboards
- How can drag forces such as water resistance or air resistance be reduced?
Streamlining/use streamlined shapes
- If you’re talking about how much of a substance there is, are you talking about Mass or Weight?
Mass
- If you’re talking about a force, are you talking about Mass or Weight?
Weight
- If you’re talking about something measured in Newtons, are you talking about Mass or Weight?
Weight
- If you’re talking about something that changes from planet to planet, are you talking about Mass or Weight?
Weight
- If you’re talking about the kg, are you talking about Mass or Weight?
Mass
- If you’re talking about the Newton/N, are you talking about Mass or Weight?
Weight
- If you’re talking about something that doesn’t change from planet to planet, are you talking about Mass or Weight?
Mass
- Remember that Weight = Mass x Gravitational Field Strength. If Mass = 1kg and Gravitational Field Strength = 10 N/kg, what is Weight?
Weight= 1 x 10 = 10 N
- Remember that Weight = Mass x Gravitational Field Strength. If Mass = 0.1kg (100g) and Gravitational Field Strength = 10 N/kg, what is Weight?
Weight= 0.1 x 10 = 1 N
- Remember that Weight = Mass x Gravitational Field Strength. If Mass = 0.2kg (200g) and Gravitational Field Strength = 10 N/kg, what is Weight?
Weight= 0.2 x 10 = 2 N
- Remember that Weight = Mass x Gravitational Field Strength. If Mass = 2kg and Gravitational Field Strength = 2 N/kg, what is Weight?
Weight= 2 x 2 = 4 N
- The Moon has a gravitational field strength of 1.6 N/kg whereas Earth has a gravitational field strength of 9.8 N/kg? What does this tell us about the relative mass of the Earth and the Moon?
The Earth has more mass than the Moon
- Why do surfaces that feel smooth still have friction?
Even smooth surfaces have microscopic hills and valleys (which resist movement)
- What force causes surfaces to wear away over time?
friction
- In addition to wearing away surfaces what other effect does friction cause when rubbing two objects together?
A rise in temperature
- Describe 2 uses of friction between solids
Without friction our feet would not be able to grip the road and we would be unable to walk / Friction is important in helping objects to slow down safely using brakes / [Also to strike a match]
- Describe a benefit of air resistance
Air resistance is the force that parachutes make use of to slow down someone who is falling from an aeroplane
- Why doesn’t a rocket in space need to use its engine to keep moving?
There is no friction or air resistance in space to slow it down. [Gravity is not zero in space]
- State the equation for speed
Speed = Distance/Time
- When distance is measured in metres and time is measured in seconds, what is speed measured in?
m/s
- Calculate the speed of an object moving a distance 10 m in 2 s.
Speed = Distance/ Time= 10 /2 = 5 m/s
- What word is used to describe an object that is speeding up?
Acceleration or accelerating
- For a spring what do we call the stretched length minus the unstretched length?
Extension
- What is the name of the law that springs obey? The law says that a spring’s extension doubles when the force doubles or extension is directly proportional to the stretching force.
Hooke’s Law
- Describe a risk assessment for the spring experiment
Hazard: Spring could break or come loose / Risk: damage eye / Precaution: Wear safety goggles