AS Physics - Mechanics (AQA) PROCTORED EXAM

What's the difference between a scalar and a vector? - ANSWERSA scalar quantity has only size, while a vector quantity has size and direction. What name is given to a vector formed by adding vectors together? - ANSWERSThe resultant vector If a body's in equilibrium, what's the sum of all the forces acting on it? - ANSWERSThe sum of all forces acting on a body in equilibrium is 0. Explain what equilibrium means in the context of a moving object. - ANSWERSFor a moving object in equilibrium there is no resulting force, so the object will continue to move at a constant velocity. What is a moment? - ANSWERSA moment is the turning effect of a force around a turning point. What name is given to a pair of forces of equal size which act parallel to each other, in opposite directions? - ANSWERSA pair of forces of equal size which act parallel to each other but in opposite directions is called a couple. What is the centre of mass of an object? - ANSWERSThe centre of mass of an object is the single point that you can consider its whole weight to act through. Where is the centre of mass in a uniform regular solid? - ANSWERSAt the centre of the object. What kind of motion does a curved displacement-time graph show? - ANSWERSA curved line on a displacement-time graph shows acceleration (or deceleration). What kind of motion does a straight line on a displacement-time graph show? - ANSWERSA straight line on a displacement-time graph shows constant velocity. What does the rate of change of gradient on a displacement-time graph represent? - ANSWERSAcceleration. What does the gradient of a velocity-time graph tell you? - ANSWERSAcceleration. How is uniform acceleration shown on a velocity-time graph. - ANSWERSStraight line. What the area under a velocity-time graph tell you? - ANSWERSDisplacement. How is non-uniform acceleration shown on a velocity-time graph. - ANSWERSCurved line. How would you find velocity from an acceleration-time graph? - ANSWERSThe area under the graph How would constant velocity appear on an acceleration-time graph? - ANSWERSStraight horizontal line. What does negative acceleration on an acceleration-time graph show? - ANSWERSdeceleration What is Newton's first law of motion - ANSWERSThe velocity of an object won't change unless a resultant force acts on it. This means a body will stay still or move in a straight line at a constant speed unless there's a resultant force acting on it. What is Newton's second law of motion - ANSWERSResultant force = mass x acceleration. This means a larger force acting on an object causes a larger acceleration, and a larger mass means a smaller acceleration for a given force. What is Newton's third law of motion - ANSWERSIf an object A exerts a force on object B, then object B exerts an equal but opposite force on object A. This means every action has an equal and opposite reaction. What's the only force present in free-fall motion? - ANSWERSWeight What's free-fall motion called when the object is given an initial velocity? - ANSWERSProjectile motion What is meant by friction and drag? - ANSWERSFriction is a force that opposes motion. Drag is the name given to friction caused by a fluid. In what direction a frictional force act? - ANSWERSOpposite direction to motion What is the difference between an elastic and an inelastic collision? - ANSWERSAn elastic collision is one where linear momentum and kinetic energy are conserved. An inelastic collision is one where linear momentum is conserved, but kinetic energy is not. What are the units of impulse? - ANSWERSNs What is the rate of change of momentum of a body falling freely under gravity equal to? - ANSWERSWeight The force acting on an object is equivalent to... - ANSWERSthe impulse it receives per second. Name three features included in cars that are designed to protect passengers in a crash, and explain how they help. - ANSWERSCrumple zones at the front and back of cars crumple up and deform plastically on impact. This causes the car to take longer to stop, increasing the impact time and decreasing the force on the passengers. Seat belts stretch slightly increasing the time taken for the wearer to stop. This reduces the forces acting on the chest. Air bags slow down passengers more gradually, and prevent them from hitting hard surfaces inside the car. What's transferred when work is done? - ANSWERSEnergy Power is the rate of doing what? - ANSWERSPower is the rate of doing work What does the area under a force-displacement graph represent? - ANSWERSThe work done. What's the principle of conservation of energy? - ANSWERSEnergy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change.