3. Forces Flashcards
A force can change an objects:
* Speed
* Shape
* Direction
What is the definition of mass?
Mass is a measure of how much matter is contained in an object.
What are the units of mass?
Kilograms (kg)
What is the definition of weight?
Weight is a force exerted on an object’s mass due to gravity.
What are the units of weight?
Newtons (N)
What is meant by the term ‘gravitational field strength’?
Gravitational field strength is the force experienced per unit mass by an object in a gravitational field.
What are the units of gravitational field strength?
Newtons per kilogram (N/kg)
What is the gravitational field strength on Earth?
On Earth, g = 9.8 N/kg
How do you rearrange W = mg to calculate mass?
m = W/g
What is friction?
Friction is a force that opposes the motion of an object.
Which direction does friction act in
Friction ALWAYS acts in the opposite direction to the motion of the object.
What type of energy is produced when friction acts on an object?
Heat energy
State an example of where friction might be useful and how it could be increased.
- Bring a car to a stop - use a deeper tyre tread.
- Starting a fire with a stick - push down on the stick more to push the surfaces closer together.
State an example of where friction is not useful and how we can decrease it.
- Hinges of doors - we can lubricate the hinge with oil to separate the surfaces.
- Competative cycling - cyclists crouch to reduce their surface area and reduce air resistance.
What is the name of the upwards force which keeps the wrecking ball in place?
Tension
What is the name of the force which acts upwards in this diagram?
Reaction Force
What are the units of acceleration?
Metres per second squared (ms-2)
If I know an objects mass and the acceleration, how do I calculate the force which caused the acceleration?
F = ma
What is the name of the missing force?
Thrust
Calculate resultant force
400 N to the right
This is a Newton Pairs question.
When walking, your shoe exerts a force on the ground. What is the reaction force to this?
The reaction force is the force of the ground pushing back up on the shoe.
A poop is dropped from rest out of a plane. It is initally accelerates, but eventually travels at a constant speed. What is the name of this speed?
Terminal Velocity
What is the name of the force acting downwards as the apple falls from the tree?
Weight
(DO NOT SAY GRAVITY!!!!)
State Newton’s first law of motion.
When balanced forces (or no forces) act on an object, it remains at rest, or continues to move at constant speed in a straight line.
You should be able to regurgitate this definition.
