SP2- Motion and forces Flashcards
(38 cards)
What is the difference between scalar and vector quantity’s
A vector quantity is something that can be measured. Scalar quantities only have a magnitude or size
Define a resultant force
When two or more forces act on an object, the resultant force can be found as it is the overall force acting on the object by subtracting the individual forces from each other.
What is newtons first law?
According to Newton’s first law of motion, an object remains in the same state of motion unless a resultant force acts on it. If the resultant force on an object is zero, this means:
a stationary object stays stationary
a moving object continues to move at the same velocity (at the same speed and in the same direction)
What is the effect of a non-zero resultant force on moving and stationary objects
Forces do not add to zero → motion will change.
Describe circular motion at constant speed as a changing velocity and hence as an acceleration
When an object moves in a circle at a constant speed its velocity (which is a vector) is constantly changing. Its velocity is changing not because the magnitude of the velocity is changing but because its direction is. This constantly changing velocity means that the object is accelerating (centripetal acceleration)
Describe the force needed to keep an object moving in a circular path.
Centripetal force
Give some examples of objects moving in circular paths and the type of centripetal force involved.
Roundabout in a motorbike-friction
Bucket of water swung on string- tension
Moon orbiting the earth- gravity
Describe the difference between mass and weight.
The mass is essentially “how much stuff” is in an object. … Weight: There is a gravitational interaction between objects that have mass.
List the factors that determine the weight of an object.
The weight of any object is affected by three factors which are the object’s mass, the planet (the place) where the object exists, the distance between the object and the centre of the planet.
Recall the equation for calculating weight.
weight=mass x gravitational field strength
Describe how weight is measured.
To make a measurement of weight, we have to measure the force pulling the object towards the centre of the Earth. We do this by balancing it with a known force. If the object is stationary, Newton’s third law then tells us that the known force is the same as the weight.
Describe how the weight of an object is affected by gravitational field strength.
The weight of an object and its mass are directly proportional. For a given gravitational field strength, the greater the mass of the object, the greater its weight. Weight can be calculated using the equation: weight = mass × gravitational field strength.
Describe what an acceleration is.
Acceleration, rate at which velocity changes with time, in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down.
List the factors that affect the acceleration of an object.
The mass of the object and the amount of the force applied to it.
Recall the equation that relates the factors affecting acceleration.
Acceleration= Force/Mass
(A=F/M)
(F=MA)
(M=F/A)
Explain what inertial mass means.
Inertial mass is a mass parameter giving the inertial resistance to acceleration of the body when responding to all types of force. Gravitational mass is determined by the strength of the gravitational force experienced by the body when in the gravitational field g.
Describe what Newton’s Third Law says
According to Newton’s third law of motion, whenever two objects interact, they exert equal and opposite forces on each other. This is often worded as ‘every action has an equal and opposite reaction’.
Recall the meaning of ‘equilibrium situation’
When all the forces that act upon an object are balanced, then the object is said to be in a state of equilibrium
Identify action–reaction pairs in familiar situations.
A swimmer swimming forward
A ball is thrown against a wall
A person pushes against a wall (action force), and the wall exerts an equal and opposite force against the person (reaction force).
Distinguish between action–reaction pairs and balanced forces.
Balanced forces are equal and opposite forces that act on the same object. That’s why they cancel out. Action-reaction forces are equal and opposite forces that act on different objects, so they don’t cancel out. In fact, they often result in motion.
Describe how objects affect each other when they collide.
When objects collide, they will exert equal and opposite forces on each other all the time they are in contact. This means that the objects will each have the same size force acting for the same amount of time.
Describe the factors that affect the momentum of an object.
Momentum is affected by the mass of the object and its velocity
Calculate the momentum of moving objects
momentum=mass x velocity
p=mv
Describe examples of momentum in collisions.
Momentum is conserved in collisions and explosions . Conservation of momentum explains why a gun or cannon recoils backwards when it is fired. When a cannon is fired, the cannon ball gains forward momentum and the cannon gains backward momentum. Before the cannon is fired (the ‘event’), the total momentum is zero.
