Past papers- 1. forces, motion and energy Flashcards

1
Q

The density of steel is 7800kg/m3 and the density of water is 1000kg/m3. Explain why the ship floats in the water.

The containers with the greatest mass are loaded near the bottom of the ship. State and explain the effect on the stability of the ship of loading the containers in this way

Define the unit kWh

A

ship is not solid steel / there are air spaces in ship (average) density of ship is less than the density of the water

the centre of gravity is lower and so the ship is more stable

energy transferred in one hour at a rate of transfer of 1 kW

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe what happens to the velocity of the motorcyclist as she travels around the bend at constant speed.

Explain why there must be a resultant force on the motorcyclist as she travels around the bend.

A
  1. (velocity) changes (as direction of motion changes) OR direction (of velocity) changes
  2. because there is an acceleration / change in velocity / change in direction / change in momentum (which needs a
    resultant force)

motorcyclist accelerates / changes momentum (because velocity / direction changes)

(resultant) force is perpendicular to the motion (of the motorcycle) OR a∝F

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain, in terms of forces, the changes in motion which occur from when the parachutist leaves the hot-air balloon

A

(initially there is acceleration due to) weight OR gravitational force OR unbalanced force / resultant force / downward force

(then) air resistance increases as speed or velocity increases

(as air resistance increases) resultant force downwards decreases OR acceleration decreases

constant speed when air resistance = weight / gravitational force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

As the student catches the ball, she moves her hands backwards. Explain the effect of this action on the student’s hands.

A

longer time (of impact / contact) AND smaller force (on them)
OR
longer time (of impact / contact) AND does not hurt as much

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

State and explain whether each of the following methods of electrical power generation is renewable.

(i) power generation in a nuclear power station

(ii) power generation from waves in the sea

A

non-renewable- (nuclear) fuel is used up

renewable- waves will always continue OR produced by wind which will always continue OR nothing used up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Explain how speed-time graph shows that there is no resultant force

A
  • Line on graph is horizontal / gradient is zero
  • (therefore) no acceleration / speed is constant
  • (resultant) force causes / is proportional to acceleration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

State two environmental benefits of the electrically powered bicycle

A

less noise OR no noise

less OR no air / gaseous pollution (from the bicycle) OR does not produce acid rain

(the bicycle) uses no / less fossil fuel

does not contribute to greenhouse effect OR does not release CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Suggest why, in normal use, the car needs to be recharged after travelling less than 390km.

A

(repeated) acceleration / deceleration / use of brakes /varying speed
motion uphill / uneven road surface
cold weather / headwind

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

State one disadvantage of hydroelectric power schemes.

State all renewable source of energy

State all sources which derives its energy from the Sun.

A

damage to habitats (for fish) / construction is expensive / droughts / flood risk if dam bursts

hydroelectric/ biofuel / wind / geothermal / tidal / solar / wave

  • fossil fuel / named fossil fuel
  • biofuel / wood / crops
  • hydro
  • wave
  • wind
  • solar cell / panel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Both of the blocks now move at a constant speed of 0.60m/ s until block B hits the
ground and the thread becomes loose.
Explain the energy change that takes place in block A after block B stops moving

A

kinetic energy (of block A) decreases

thermal / internal energy produced / increases (due to friction)

friction mentioned or block slows down / decelerates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State what is meant by the limit of proportionality

A

beyond where the extension is not directly proportional to the load or (point) where extension stops being directly
proportional to the load or point up to which extension is directly proportional to the load

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe how to use a stop-watch to determine the time period of the pendulum.

A

(use stop-watch to) time oscillations

(use of fiduciary) aid to determine a complete cycle

(use of) multiple oscillations AND division (to determine period)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

State what is meant by the moment of a force about a point.

Define the moment of a force.

A

(moment of a force) is the turning effect (about a point / pivot)

force × perpendicular distance from pivot / point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

State one advantage and one disadvantage of tidal power as an energy resource.

State the main source of energy for tidal energy

A

advantages:
* renewable
* reliable or predictable
* running cost low
* does not produce (harmful) pollution.

disadvantages:
* (high) cost of construction
* possible effects on (marine) life
* not available all day
* power produced doesn’t always match with peak demand
* limited number of sites
* maintenance difficult /increased corrosion (because underwater).

Moon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The power station uses some of its waste thermal energy to heat water for houses in a nearby
town. State one problem of using waste energy in this way if the power station is far from the town.

Suggest a way of reducing this problem

A

water will cool (too much) / thermal energy lost (during transfer)

lag/insulate (pipes) OR transport in a poor conductor of thermal energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

State environmental consequences of burning coal to generate electricity.

A
  • air pollution / harmful gases / acid rain
  • CO2 / greenhouse gases / contribution to global warming
  • not renewable
  • damage from mining / drilling or any valid environmental consequence of transport of coal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain, in terms of the forces acting on the skydiver as he opens his parachute

Explain why opening the parachute cannot reduce the speed of the skydiver to zero

A
  1. (deceleration because) upward force greater than weight or upward resultant force

air resistance decreases (with decreasing speed / with time)
or deceleration decreases or resultant (upward) force decreases

(until / finally) weight equals air resistance or forces balance or at terminal / constant velocity / speed

  1. at zero speed there is no air resistance
    weight / downwards force is (still) acting or there is (now) a resultant force (downwards at zero speed)

OR

forces balance at a speed greater than zero
speed cannot decrease / no deceleration once forces balance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

As the trolley moves across the rough surface, it slows down and stops. Explain, in terms of the work done, the energy change that takes place as the trolley slows down.

A

work done against / due to / because of friction or kinetic energy (of trolley) used to do work

kinetic energy decreases (to zero)

thermal energy produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Explain why the pump must exert an increasing pressure on the oil as the depth of the oil increases

A

pressure due to increased height of oil in cylinder or pressure in liquid increases as depth increases

to keep the upwards force constant or to lift the (extra) oil
or to counteract / oppose the increased pressure / force / weight of the oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Explain, in terms of the momentum of the molecules, why there is a pressure at the inner surface of the balloon.

Explain why the volume of the air in the balloon decreases as the temperature decreases.

A

they / molecules collide with inner surface
momentum (of a molecule) changes / reverses
force exerted / impulse
force spread over area / surface or p =F / A

molecules move more slowly / have less kinetic energy
pressure (inside balloon) decreases or pressure is directly proportional to temperature or p∝T
volume is directly proportional to temperature or V∝T
molecular collisions less frequent
molecular collisions less violent / hard / exert smaller impulse
water / external pressure compresses balloon or
water pressure greater (and balloon compressed)

20
Q

The train took 80s to reduce its speed from 84m/s to 42m/ s. Explain why, with the same braking force, the train takes more than 80s to reduce its speed from 42m/ s to zero.

A

less drag / air resistance (at slower speeds)

21
Q

The angle the bus makes with the horizontal is gradually increased until the bus begins to topple to the left.
Explain why the bus begins to topple.

There are 30 passengers in the upper compartment of the bus and 2 passengers in the bottom compartment of the bus. State how this affects the stability of the bus and the reason for this

A

a. line of action of the centre of mass falls outside the base of the bus
anticlockwise moment is greater than clockwise moment

b. bus more likely to fall over / topple / less stable
(line of action of) centre of mass may fall outside (the base of) the bus

22
Q

Suggest why some of the kinetic energy of the air that passes through the circular area swept out by the blades is not converted into electrical energy.

A

Speed of air not reduced to zero (in passing through turbine) OR some air passes through blade area without change of speed OR without hitting blades
OR not all k.e. of air transfers to blades
OR air retains some of its k.e.
OR friction in bearings of blades

23
Q

State three ways in which a force may change the motion of the object.

A

Accelerate or increase speed OR Decelerate or decrease speed OR Change speed

Change direction OR causes rotation

24
State the principle of the conservation of momentum. Explain how the principle of the conservation of momentum applies to the accelerating rocket and the exhaust gases.
i. no external forces OR isolated system sum of momenta / (total) momentum remains constant ii. rocket gains (upward) momentum (ejected) gas gains equal (quantity of) momentum in opposite direction OR momentum of gas decreases by equal amount
25
State what is meant by centre of mass. The concrete block is removed. The sign and support post rotate about point P in a clockwise direction. State and explain what happens to the moment about point P due to the weight of the sign as it rotates.
(the point) where (all) the mass can be considered to be concentrated (moment / it) increases perpendicular distance (between P and line of action of) W increases
26
State and explain, in terms of molecules, any change in the pressure of a gas when the volume is reduced at a constant temperature.
pressure increases * molecules travel shorter (average) distance between collisions with walls NOT molecules change speed * molecules hit walls more often OR more collisions (per unit area) with walls * {greater force OR greater (rate of) change of momentum of molecules} per unit area on walls
27
The brakes of the model are released. State and explain the direction of the acceleration of the model State and explain any change in the magnitude of the initial acceleration if the brakes are first released when the tank is nearly empty
1. (acceleration is) to right/backward Explanation: force (from water OR on model) to right /backwards OR acceleration in same direction as force (from water OR on model) 2. (acceleration) more (when empty) mass less (and force is constant) as F=ma / Newton’s 2nd law / change in momentum
28
Dock walls sometimes have the pillars replaced with rubber car tyres. Explain how this reduces the possibility of damage when a boat docks.
smaller force (on dock/ship) because increases time of collision OR increased distance of collision (on the dock/ship)
29
Define impulse
force × time (for which it acts)
30
Describe how the molecular structure of the liquid metal differs from that of the solid metal.
(molecules /they) have an irregular arrangement / not ordered/random arrangement (molecules /they) are (slightly) further apart (on average) (molecules /they are) not fixed in place
31
arrangement and forces in solid, liquid & gas
Solids – molecules in lattice arrangement solids – strong forces between molecules liquids – molecules not fixed in place OR molecules have an irregular arrangement OR molecules (slightly) further apart (on average) than in solids OR spaces between the molecules liquids – (average) forces too weak to keep molecules in a definite pattern OR forces just enough to hold molecules in the bulk of the liquid gases – molecules far apart gases – weak / no forces between molecules (except during collisions)
32
Explain why the gravitational potential energy (g.p.e.) of the object increases with height
(Because g.p.e. is) the work done by the force OR the force × the distance that the object rises OR mgh and height is greater
33
movement of the molecules in solid and gas
(Molecules) vibrate random/haphazard/in all directions AND with high speed freely zig-zag in straight lines
34
The actual height reached by the bullet is less than the value calculated. Explain, in terms of the forces acting on the bullet, why this is so As the bullet rises through the air, its kinetic energy decreases. State what happens to this energy
(force of) air resistance acts downwards adds to gravitational force/resultant force increases/deceleration increases/deceleration > g (kinetic energy) to gravitational potential energy (kinetic energy) to thermal/internal energy
35
State the conditions which must be true if the object (i) does not accelerate (ii) does not rotate.
No resultant force /net force OR Forces are balanced OR Forces in opposite directions are equal OR Forces cancel no resultant/ net moment / torque/turning effect OR (Sum of) clockwise moments = (sum of) anticlockwise moments
36
Suggest one reason why there is a delay before the temperature of the water increases to 23 °C as surrounding air increases to a temperature above 23 °C. Explain why, after this delay, bulb B sinks. Assume the bulbs do not expand
Glass is a poor conductor of heat OR glass conducts heat at a slow rate OR water has a high (specific) heat capacity The water expands OR separation of water molecules increases , The water becomes less dense , Bulb B now has a greater density than the water (and sinks) OR Weight of bulb B more than buoyancy forces /upthrust
37
State what is meant by the term weight. Explain what is meant by mass. difference bw the two
(Weight is) force/pull of gravity (acting on an object) (Measure of) quantity / amount of matter OR (property) that resists change in motion / speed / momentum OR measure of a body’s inertia weight has direction / mass does not weight is a vector / mass is not weight varies / mass does not mass is amount of matter weight is a force / mass is not
38
Describe a process by which electrical energy is obtained from the chemical energy stored in this fuel. Explain why the Sun is the source of the energy stored in the fuel. Explain whether the process in (a) is renewable
any three from five: * thermal energy / heat (from fuel) * water / steam / gas heated OR steam produced * (steam / gas) turns / moves / drives turbine * (turbine) turns / moves / drives generator * 2 correct energy transfers sun is energy source for plants / living matter (to grow) plant / animal (remains compressed) into fuel OR carbon / chemical energy stored / trapped in plant / animal (remains) not renewable (as fuel is consumed) could only be replaced over very long time period (e.g. clearly > 50 years)
39
Describe and explain a danger to a driver of not wearing a safety belt during a sudden stop.
(Without seat belt, driver:) e.g. keeps moving (forwards)/ does not stop/ has inertia/ has momentum (Driver) hits steering wheel/windscreen/ dashboard
40
The deceleration of the dummy is less than the deceleration of the passenger compartment. Explain why this is of benefit for the safety of a passenger.
Force/ impact on passenger or dummy less (than without seat belt/airbag) Passenger less likely to be injured/ hurt/ damaged
40
Suggest why the skier bends his body
to reduce (air) resistance/ drag OR to lower centre of mass to increase acceleration/ speed/resultant force OR smaller (frontal) area/ better aero(dynamic) shape OR to improve stability / balance
41
The force needed to open the lid in water is not equal to the value calculated. Suggest two reasons for this.
weight of lid (there is a) pressure inside box OR upthrust on lid moment of force changes friction (of hinge) drag of water
42
Explain the benefit of increasing the time of contact for the people in the car
(increased time causes) decreased rate of: change of momentum/acceleration/deceleration/impulse ÷ time smaller forces on people/less injury
43
The tanker sails out onto a calm sea. The density of sea-water is greater than the density of river water. State and explain any change in the depth of the bottom of the tanker below the surface.
Weight of tanker has to be equal to upward force of water Depth (below surface) is /becomes less OR Tanker rises (Tanker rises) because pressure /force on bottom of tanker is greater OR because upthrust greater OR At same depth as in river, pressure / force on bottom of tanker is higher so tanker rises
44
State one advantage and one disadvantage of generating electrical power in nuclear power stations compared with electrical power generated using wind turbines
advantage – one from: * Continuous supply of energy * not affected by the weather OR not affected by wind strength * produces large amounts of energy disadvantage – one from: * resources finite / not renewable * cost / difficulty of building / cost / difficulty of decommissioning * danger if any leak of radiation * produces hazardous / dangerous waste OR difficulty of storage of used radioactive material OR nuclear waste must be stored for a long time
45
State two renewable sources of energy. Source 1 ........................................................ Source 2 ........................................................ (ii) State one social, economic or environmental disadvantage of one of your answers to
solar, wind, water, hydroelectric, waves, tidal, geothermal Energy for wind / waves / Sun not always available Cost of building wind turbines or tidal barrages or hydroelectric dams Wind turbines affect the scenery of some areas Solar (farms) use (agricultural) land / takes up a lot of space
46
(a) Describe a renewable process by which electrical energy is obtained from the energy stored in water. You may draw a diagram in the space. (b) Explain why the process described in (a) can be regarded as renewable. (c) Explain whether the Sun is the source of the energy stored in the water in (a).
Hydroelectric 8(a) Hydroelectric named OR water from behind dam K.E. of (falling) water used / P.E. of stored water Turbine / waterwheel / paddle wheel operated (Turbine) turns / drives a generator (that produces electricity) 8(b) Rain (fills lakes in high places) Cause of rain is the Sun, so renewable 8(c) Sun evaporates water from sea etc. to fall (later) as rain Sun is the source of energy. Tidal flow 8(a) Tides / tidal flow named K.E. of water used Turbine / waterwheel / paddle wheel operated (Turbine) turns / drives a generator (that produces electricity) 8(b) Moon (and Sun) causes tides Moon (and Sun) permanently in place, so renewable 8(c) Attraction due to Moon’s (and Sun’s) gravity causes tides Sun is a source of (part of) the energy OR Sun is not the primary source of energy
47
The use of wind turbines on a large scale has environmental and economic impacts. Describe one environmental impact and one economic impact.
relevant environmental pro or con, e.g. no /less air pollution, no / less greenhouse gases OR visual / noise impact / pollution, injure birds, deforestation, conserves non-renewables relevant economic pro or con, e.g. no fuel cost or expensive to install (compared to other types of generation)