AQA A level Physics Mechanics exam fully solved & updated

Explain what is meant by an inelastic collision - answer-where kinetic energy is not conserved State, in words, the relationship between the force acting on a body and the momentum of the body - answer-Force is the rate of change of momentum State two quantities that are conserved in an elastic collision - answer--momentum -kinetic energy Use Newton's laws of motion to explain how the molecules of a gas exert a force on the wall of a container - answer--force is exerted on molecule by wall -to change its momentum - molecule must exert an equal but opposite force on wall -in accordance with Newton's second or third law An apple and a leaf fall from a tree at the same instant. Both apple and leaf start at the same height above the ground but the apple hits the ground first. use newton's laws to explain why the leaf accelerates at first then reaches a terminal velocity. - answer--Newton's second law stares that F=ma -As there is a large weight and little air resistance at first, there is a large acceleration -As the weight begins to get balanced out by the air resistance, the resultant force decreases which means that acceleration decreases -When the acceleration is constant, it has reached terminal velocity Galileo used an inclined plane to investigate the motion of falling objects. Explain why using an inclined plane rather than free fall would produce data which is valid. - answer--Free fall is too quick -No reliable method to time free fall State two vector quantities - answer--Velocity -acceleration -force State two scalar quantities - answer--speed -distance -mass State the difference between a scalar quantity and a vector quantity - answer-Vector quantities have both magnitude and direction but scalar quantities only have magnitude Explain what is meant by centre of gravity - answer-The point at which the mass of the system can be considered to be concentrated Define the moment of a force - answer-moment=force x perpendicular distance State the Principle of moments - answer-Sum of clockwise moments = sum of anti-clockwise moments In an experiment to measure the power output of a motor, the motor is used to lift a metal block vertically at constant speed. Describe an experiment to check whether the speed of the rising mass is constant. - answer--Mark out equal distances along height being raised -Measure time taken to travel each of these distances -Times should be equal In an experiment to measure the power output of a motor, the motor is used to lift a metal block vertically at constant speed. explain how the output power of the motor is calculated, stating what measurements need to be made. - answer--Find work done by motor from gain in potential energy of metal block -Divide work done by time to find power -Measurements: mass of block, height block has risen and the time taken State one advantage and one disadvantage of wind power in comparison to fossil fuel - answer-Advantage: doesn't cause air pollution Disadvantage: Depends on the wind What is meant by the word 'couple' - answer-A couple is a pair of forces of equal size which act parallel to each other, but in opposite directions What is given by the slope of a displacement-time graph - answer-velocity How do you calculate acceleration from a velocity-time graph - answer-the gradient How do you calculate the displacement travelled from a velocity-time graph? - answer-Area under graph What does area under an acceleration-time graph tell you? - answer-change in velocity