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38 Cards in this Set

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 What are Scalar Quantities? Scalar quantities have magnitude but no direction. Some examples of Scalar Quantities? Examples of Scalar Quantities mass, time ,speed, distance, volume etc What are Vector Quantities? Vector quantities have both magnitude and direction. Some examples of Vector Quantities? Examples of Vector Quantities displacement, velocity, acceleration What is Distance? Distance is concerned with how much ground is covered regardless of direction. Speed is the rate of change of distance What is Displacement? Displacement is distance in a specific direction or the change in position of an object. What is Velocity? Velocity is the rate of change of displacement. What is Acceleration? Acceleration is the rate of change of velocity. Formula for Average Speed? Formula for Average Velocity? Average speed = total distance travelled/ total time taken Average velocity = change in total displacement/ total time taken for change Acceleration = change of velocity/ time The instantaneous speed is the speed at any instant Instantaneous velocity is the velocity at any given instant. Symbols used in equations of motion. Let the initial velocity of an object be u ms-1 Let the final velocity of an object be v ms-1 Let acceleration (assumed uniform) be a ms-2 Let the interval for the motion be t s Let the displacement of the object be s m Acceleration= Acceleration(a) = change of velocity (v-u)/ time(t) OR v=u+at Displacement= Displacement = average velocity x time An object accelerates uniformly from 10ms-1 to 30ms-1 in 5s. What is: a)The acceleration of the object? b)The distance covered in the 5s? A) 30-10/5=4 B) Distance = Rate x Time 4 x 5 = 20 meter A car is travelling at 60ms-1 when the traffic light turns red. The car decelerates at 6ms-2 . a)How long does the car take to stop. b)How far from the lights must the driver start braking in order to not overshoot the lights. A) t= u-v/a 60-0/6=10s B) x= (u+v)t/2 ((60-0)/2) x 10 What is a Projectile Motion? A projectile is an object which ,given an initial velocity continues in motion by its own inertia and is influenced only by the downward force of gravity. Case 1: no gravity The object will continue to move with the same speed and in the same direction Case 2: gravity The object will continue to move to horizontally while falling under gravity. There is no force in the horizontal direction so there is no acceleration in that direction. Producing a parabola When an object is going up gravity is acting negatively it slows the object down. When the object is going down gravity acts positively it speeds the object up. Gravity has no impact on the horizontal component of velocity of the object it remains constant. Newtons first law? An object at rest remains at rest and an object in motion remains in motion until acted upon by an unbalanced force. Newtons second law? Force is equal to the rate of change of momentum. F=ma F= m(v-u)/t Newtons third law? For every action there is an equal and opposite reaction. A constant force changes the velocity of a 100kg sprinter from 4.0ms-1 to 6ms-1 in 1.0s. Calculate a.The acceleration of the sprinter during this time. b.The magnitude of the force A) Acceleration = v-u/t 6-4/1 = 2 B) F=ma 100KG x 2ms-1 = 200 Linear momentum Linear momentum of an object (p) is the product of its mass and its velocity. Its units are kgms-1 . Momentum is a vector quantity. Impulse? Impulse is equal to Force x time Fxt= mΔv this is called the impulse-momentum equation The principle of conservation of linear momentum states? The principle of conservation of linear momentum states that the total linear momentum of a system remains constant during collisions. In a head on collision between x and y which would have the positive and negative velocity? In the head on collision between x and y we assign objects moving to the right with a positive velocity and an object moving to the left with a negative velocity. mxvx –myvy = -mxv`x + myv`y What is an elastic collision? Elastic : momentum is conserved, kinetic energy is conserved and total energy is conserved. Particles approach at a given speed and after collision they recede with the velocity vector having the same magnitude but different sign. What is an elastic collision? Inelastic collisions: momentum conserved ,kinetic energy not conserved and total energy is conserved. What is work? An object which has the ability to do work is said to have energy. Work is done when a force acts upon an object and displaces it . The unit for work and energy is the JOULE J. Work= W= F x dCos θ F is the applied force d is the displacement θ is the angle between the force and displacement vectors Work again? When force and displacement are in the same directions θ = 0 Cos θ = 1 W =Fxd What is energy? The energy acquired by objects on which work is done is known as mechanical energy. This energy is possessed due to Its stored energy (potential energy) Its motion(kinetic energy) Gravitational potential energy? Gravitational potential energy Energy that an object has because of its height above some reference point usually ground Elastic potential energy? Elastic potential energy Energy stored in some compresses or stretched elastic materials eg. wound up clock, compressed spring. The amount of potential energy stored is related to the extent of the deformation of the material. Chemical potential energy? Chemical potential energy Energy stored in chemical compounds eg bonds in gasoline molecules Gravitational potential energy formula? Ep =mass (kg)x acceleration due to gravity(Nkg-1) x height(m) Ep = mgh 45 What is Kinetic Energy? Kinetic energy This is the energy an object has because it is moving. Kinetic energy (J) = ½ x mass x velocity2 Difference between potential and kinetic energy? When an object is above ground the potential energy is maximum and kinetic energy is zero. Opposite for kinetic energy At the instant before the object strikes the ground all its potential energy has been changed to kinetic energy. What is power? Power is the work done or energy converted per unit time. Power Formula? Power = force x displacement/time taken = Workdone/ time taken What is power measured in? Power is measured in Watts(W)