Section 3 - Mechanics and Materials Exam Questions Flashcards Preview

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Flashcards in Section 3 - Mechanics and Materials Exam Questions Deck (47)
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State two conditions for a rod supported by two wires to be in equilibrium (2)

Resultant force zero
Resultant torque about any point zero


State three vector quantities (3)



State three scalar quantities (3)



State the three forces that will act on a helicopter that is moving horizontally (3)

Air resistance


How can force vectors be arranged to show that an object has constant velocity? (2)

Closed triangle of vectors
Forces are in equilibrium


What is the difference between a vector quantity and a scalar quantity? (1)

Vector has a direction
Scalar does not


What is meant by centre of gravity? (1)

The point in a body where the weight of the object appears to act


Define the moment of a force (1)

Product of the force and the perpendicular distance from the line of action of the force to the point


State the principle of moments (2)

Sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments for a system in equilibrium


State and explain a feature of a crane that helps prevent it from falling over when lifting heavy things (2)

Provides a sufficiently large moment in the opposite direction


A stationary car and trailer are attached by a towbar, F is the force exerted by the towbar on the trailer. What happens to the magnitude and direction of F when the car moves forward? (3)

Force must have a horizontal component
F increases in magnitude
F acts at an angle towards the car


Why would a thin card give a more accurate measurement of g compared to dropping a tennis ball? (2)

Ball's acceleration will decrease
Air resistance affects cards less


What feature of a speed against time graph would show a constant acceleration? (1)

Constant gradient


Why does an object first accelerate after being dropped then reach a terminal velocity? (4)

Weight greater than air resistance
Therefore resultant force downwards
Air resistance increases with speed
Until resultant force is zero


Why would an apple hit the ground first if dropped with a leaf? (2)

Air resistance depends on shape
Air resistance less on apple, therefore greater velocity


How can using an inclined plane rather than free fall produce valid data on investigating a falling object's motion? (2)

Freefall is too fast
No accurate method to time freefall


On a distance against time graph, how would speed at a certain time/distance be worked out? (1)

Draw a tangent


For impulse and force, determine whether each one is a vector or a scalar (2)

Impulse - vector
Force - vector


The rate of change of momentum of a body in free fall under gravity is equal to its.. (1)



On a force against time graph, what is the area under the graph equal to? (1)

The change in momentum of the body


In an inelastic collision, which quantity is not conserved? (1)

Kinetic energy


A person is kicking a football, discuss the radial force on the knee joint before impact and during the impact (2)

Before impact: radial pull on knee joint due to centripetal acceleration of boot
During impact: radial pull reduced


State the relationship between the force acting on a body and the body's momentum (1)

Force is equal to the rate of change of momentum


Use Newton's laws of motion to explain how molecules of gas exert a force on the wall of a container (3)

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 third law


A deep space probe ejects a capsule explosively, and immediately after the probe moves at a greater speed. Discuss how conservation of momentum and energy apply in this instance (6)

Momentum conserved because there are no external forces acting on the overall system
During the explosion there are equal and opposite forces acting between the probe and the capsule
Because momentum is a vector, the capsule must move along the original line of movement
Total energy is always conserved in any physical process
Energy may be converted from one form to another
In the explosion, some chemical energy is converted to kinetic energy


A ball rolls towards a footballer and is then kicked, if the ball had a higher initial speed and received the same impulse, discuss how it may differ (3)

Final speed would be lower
Initial momentum would be greater
Change in momentum is the same


A motor is used to lift a metal block vertically at constant speed. Describe an experiment to check whether the speed is constant (2)

Mark out equal distances along height being raised
Measure time taken to travel each of these distances


Explain how the output power of the motor is calculated, state any measurements made (3)

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 time taken


Describe how a trolley moving down a sloped track can have its speed measured experimentally (3)

Place piece of card on trolley of measured length
Card obscures light gate just before trolley strikes block
Calculate speed from length of time obscured


State an advantage and disadvantage of wind power in comparison to fossil fuel (2)

Causes no air pollution
Wind is intermittent