June 2002 PHY1

1.

C 1

A 1

B 1

E 1

2. Composition of alpha article

2 protons + 2 neutrons only 1

Explanation of ionize

Change nunber/Add/Remove electrons 1

Estimation of time alpha article would take to travel

Use of E = ½ mv2 1

Use of t = diameter/u 1

6.3 x 10^-18 s [ no ecf] 1

Explanation comparing speed of alpha and beta articles

Faster 1

Less massive/lighter/less weight (not smaller) 1

3. Explanation of essential difference between 2 definitions

Distance in direction of force against distance perpendicular to force 1

Correctly identifying which is which 1

Principle of moments

AP =80

,PB=32

[allow+ 1 ] [no ue ] 1

Demonstrate that moments are = equal. [allow any distance values] 1

Distance load at B raised

Use of work = force x distance / use of rngh [ beware m = 20 ] 1

Use of work out = work in / use of mgh lost = mgh gained 1

2.4x10 m 1

OR

Similar triangles/distance moved proportional to distance from pivot 1

x/6 x 10^-3 = 32/80 or equivalent 1

2.4x 10 m 1

4. Deceleration of cars

Acceleration = gradient / suitable eqn. of motion. 1

Correct substitutions [ 0.9 for t is wrong] 1

6.1 – 6.3 m s2[-ve value – 1] [ no ecf ] 1

Area under velocity -time graph

Distance/displacement 1

Shaded area

6.9 – 7.5 1

m 1

[Allow 1 mark for 5.5 – 6.1 cm .]

Minimum value of the initial separation

Both sloping lines continued down to time axis [by eye] 1

Explanation

Area between graphs is larger/B travels faster for longer/B still moving when A stops 1

Extra distance B goes is larger/ > 7.2 1

Initial separation must be larger 1

5. Experiment

2 light gates 1

Gate gives time trolley takes to pass [ not just ’the time’] 1

Speed = length of ’interrupter’/time taken 1

Or

2 ticker timers 1

dots at known intervals 1

speed = lenghth of tape / time taken 1

(ruler and clock method 1 mark max)

Total momentum of trolleys

Zero 1

It was zero initially or momentum is conserved [consequent] 1

Speed v of A

Use of momentum = mass x velocity 1

Use of mass x speed (A) = mass x speed (B) 1

1.8 m s -1 [ignore – ve signs] 1

6. Explanation of why kicking a door is more effective

Quality of written communication 1

Foot decelerates/ loses momentum 1

This takes place rapidly giving a large force by Newton 2 or equation versions [consequent] 1

Door is providing this force [consequent on mark 1] 1

Door acts on foot; by ’Newton 3’ foot acts on door 1 Max 3

7. Free-body force diagram

Normal reaction/contact force [or Nor R or push of table] upwards 1

E-M magnetic force [or magnetic attraction or pull of magnet] to right 1

Weight [or W or mg or gravitational force or gravitational attraction or pull of Earth] downwards 1

[Ignore labeled forces of action or drag] [if unlabeled – 1 each force]

Forces

Pull on earth 1

Upwards [consequent] 1

Or

Push contact / force on table 1

Downwards 1 [consequent]

Or

Force on magnet X 1

To left [consequent] 1

Precautions

Measure background radiation //shield apparatus 1

Subtract it off/ because it may vary//to eliminate background 1

Repeat the count and average 1

Because count (or emission) is random/varying 1

Source the same distance from GM on both occasions 1

Because count rate varies with distance 1 Max 3

[NB Marks must come from any TWO precautions.]

Ratio

0.88 or l. 1 [min. 2 sf] [not%] 1

Count for year 3

11 994 1

Graph

Suitable axes and scales [don’t award if factors 3, 7 used][not Bq] 1

Correct plotting of points 1

Use of curve and halving count rate 1

5.3 to 5.4 yr 1

9. Name of nuclei

Isotopes (not radioisotopes) 1

Nuclear equation

Electron numbers complete anywhere 1

Correctly balanced 1

Densest material

Sn 115 1