02 - Mechanics Flashcards
(29 cards)
At high speeds the guide pin may become disengaged from the groove.
Use Newton’s first law to explain why the car would then leave the track at a corner.
No Resultant Force is Acting on the Car
Car continues moving in straight line
Suggest why the actual speed of the car is less than the calculated speed
Energy is dissipated to heat due to friction between the wheels and track
State what is meant by work done
Force x Distance moved in the direction of the applied force
A projectile would have a greater range on the Moon than the Earth because of the lower gravitational field strength and because of the lack of an atmosphere.
Explain how each of these factors would increase the range of the projectile.
Lower Gravitational Field Strength:
lower acceleration so an increased time of flight
Lack of atmosphere:
no work done against friction
Explain why the string would not become horizontal, however great the acceleration
String always has a weight so tension needs a vertical component.
Suggest why many devices contain 3 accelerometers, arranged at right angles to each other.
to detect movement in x,y,z planes
Demonstration-
Large 7kg bowling ball pendulum on a long piece of wire released from nose of student
Precautions-
Don’t push ball - just release
Don’t move face b4 ball returns
Explain this demonstration and the need for the precautions.
Demonstration-
Total energy of the pendulum is conserved as energy transfers from GPE to KE vice versa
It cannot move higher than its starting point because that would require extra GPE
Energy is lost against air resistance so will stop the pendulum reaching its starting point
Precautions-
Pushing provides extra energy making the pendulum move higher so it will hit the student.
if the face moves forwards the ball may reach it.
Suggest a reason for inefficiency
friction
Suggest why a rubber band is used to support the arm
so that it can store elastic potential energy
state the energy transfers that occur when the string is released
Elastic Potential Energy
to
GPE + KE + Thermal Energy
explain why the distance increases as the angle of a projectile increases
the greater the angle the greater the tension
the greater the acceleration of the projectile
greater velocity of the projectile
s = ut linked to a greater range
state why replacing a projectile with a lower mass can increase the range of the projectile
F=ma
reduced mass increases acceleration for the same force applied on the projectile
Suggest one modification to the model that would also increase the range of the
projectile. Give a reason for your answer
increase tension by adding more rubber bands or stiffer rubber bands
increase vertical distance by increasing arm length or raising the device
Describe the energy transfers of a bungee jumper
Ignore any
changes that could be due to air resistance
Freefall > GPE TO KE
deceleration as the bungee rope stretches > GPE AND (KE TO EPE)
upwards motion as the bungee rope contracts > EPE TO (GPE AND KE)
The student stated that as long as the opposite poles of the magnets are facing one
another, the attractive force created should cause the toy car to start moving forward.
Explain why in practice this could never work.
Due to Newton’s 3rd Law, magnet A exerts a force on magnet B and magnet B exerts an
equal and opposite force on magnet A
The magnets are connected to the same body/each other
There will be no resultant force as the forces will balance
Suggest and explain a measure that a swimmer could use to reduce
the drag force acting on him
Wear tight fitting clothes- reduce turbulent flow
or
Keep their body as flat as possible - cross sectional area as small as possible
State and explain the effect on the motion of the iceberg if the tow ropes were
longer. Assume that the tug boat’s power output is constant.
No effect on the motion, the iceberg will travel at the same speed.
Resultant tension is the same
Explain how a lawnmower with the top section of the handle horizontal changes the minimum force required to push the lawnmower.
Force is in direction of motion so that less force needs to be applied
Kinetic energy of the wind is transferred to
electrical energy by the turbine as the blades rotate.
Explain why we can say that the wind is doing work on the blades.
Wind exerts a force on the blades, the
blades move through a distance in the direction of the force
Suggest a reason why it is not possible to usefully transfer 100% of the kinetic
energy of the wind on a wind turbine
Not all the air hits the blades
Suggest the limitations of using wind turbines to provide power
Wind doesn’t always blow, if there is no wind they don’t work as turbines need a minimum amount of wind to generate the electricity
need a large amount of wind
can’t be used in very high winds
Low power output so need a lot of turbines which take up a lot of space
Explain reasons why the projectile does not go as far as expected
Air resistance
Friction
Less energy has been transferred to the projectile
- An object is falling at TERMINAL VELOCITY
The acceleration of the object is zero
There is a resistive force acting on the object
The object has weight
- A space rocket lifts off vertically because
the exhaust gases exert a force on the rocket
