AQA AS Physics - Mechanics and Materials Exam Questions and Answers 100% Pass

AQA AS Physics - Mechanics and Materials Exam Questions and Answers 100% Pass Scalar - Answer- A unit with magnitude but no direction. Vector - Answer- A unit with magnitude and direction. What are the two methods for adding vectors? - Answer- Scale drawings and trigonometry. Free-body force diagrams - Answer- Show all the forces acting on a body, each arrow shows the size and the direction of the force. Equilibrium - Answer- The forces acting on a body are balances and it is not accelerating (it may be at rest or at a constant velocity). Moment - Answer- The turning effect of a force. Moment equation - Answer- Force x perpendicular distance from the pivot. Moment unit - Answer- Nm If the moments on an object are not balanced, - Answer- it will turn. Principle of Moments - Answer- For a body to be in equilibrium, the sum of the clockwise moments about a point must be equal to the sum of the anticlockwise moments about the same point. Levers - Answer- In a lever an effort force acts against the load force about a rigid object (the lever) attached to a pivot. Couple - Answer- A pair of equal and opposite coplanar forces (they act parallel to each other). What does a couple cause? - Answer- No resultant linear force, but a turning effect (a moment). The moment created by a couple - Answer- The size of the moment depends on the size of the forces and the distance between them. Couple equation - Answer- Moment of a couple = size of one force x perpendicular distance between the forces. Centre of mass - Answer- The point at which the mass of the object acts. Where is the centre of mass of a uniform, regular solid? - Answer- At its centre. The centre of mass can be found through... - Answer- Symmetry and experiment (hanging it and drawing a vertical line down, repeating this - where the lines cross is where the centre of mass is). How can centre of mass be used to stabilise objects? - Answer- If the line drawn downwards from the centre of mass passes within the base area, then the object will be stable. Free fall - Answer- The motion of an object undergoing acceleration due to gravity. The only force acting on an object in free fall - Answer- Weight Objects in free fall... - Answer- accelerate at the same rate. Newton's first law - Answer- An object will remain at rest or at a constant velocity as long as there is no resultant force. If the forces on an object aren't balanced, it will... - Answer- accelerate Newton's second law - Answer- The resultant force is proportional to the acceleration of the object (F = ma) Newton's third law - Answer- Each force has an equal and opposite reaction force. Friction - Answer- A force that opposes motion. Dry friction - Answer- Occurs between solid surfaces. Fluid friction - Answer- Occurs in fluids like air or water (drag, lift). The magnitude of the fluid friction force depends on... - Answer- The viscosity of the fluid, the speed and shape of the object. How does the speed of an object affect the fluid friction? - Answer- If it is moving faster, more particles will hit it per second. Frictional forces convert kinetic energy to - Answer- heat and sound. Lift - Answer- An upwards force on an object moving through a fluid. Lift acts perpendicular to... - Answer- The movement of the object, when the fluid changes direction it exerts a force on the object. Terminal Velocity - Answer- The maximum speed at which an object can fall. When does terminal velocity occur? - Answer- When the driving force is constant throughout free fall and it is equal to the frictional/drag force. Three stages of terminal velocity - Answer- The object accelerates with a constant driving force, the object moves faster and the frictional forces increase (which reduces the resultant force and acceleration), the driving force is equal to the frictional force , so there is no acceleration. Momentum - Answer- A property of a moving object which is dependant on its mass and velocity. Momentum = - Answer- mass * velocity Conservation of momentum - Answer- In a collision, the momentum before is equal to the momentum after. Elastic collision - Answer- Kinetic energy is conserved. Inelastic collision - Answer- Kinetic energy is not conserved. Momentum is always... - Answer- conserved The rate of change of an object's momentum is directly proportional to the resultant force acting on it. - Answer- Newton's second law. Newtons second law in terms of momentum - Answer- F = (delta)mv/(delta)t Impulse - Answer- Change in momentum. Impulse is the area under a... - Answer- Force-time graph Ft = (impulse) - Answer- mv - mu How do safety features in cars work? - Answer- They increase the time taken for a collision. Work - Answer- The amount of energy transferred when when moving an object against a force. Work = - Answer- F*cos(theta) Explosions - Answer- An instance of momentum where one object move