Physics Answers

QUESTION FOUR
A student cycles to school each day. He must ride over the steep hill
between his home and school. The combined mass of the bike and
student is 70kg.
He has a new speedometer and records his speed at various times as in
the table.
Time (s) 0 120 240 360 480 540 600
Speed (ms -1 ) 0 2.5 2.5 1.2 1.2 9.0 0
QUESTION FOUR ANSWERS
For Achievement you require Part (i) OR part of (ii) correct (a)
a = change in speed = 2.5 = 0.02 ms -2
Change in time 120
OR
W=Fd - correct calculation of force or distance (units not needed) or carry
through error from part (i) in F=ma
This data is shown on the grid below.
Speed (m s -1 )
10
9
8
7
6
5
4
3
2
1
0
0 100 200 300 400 500 600 700
Time (s)
(i) Calculate the acceleration of the student on his bike in the
first 120 seconds.
For Merit you require part (i) correct (a = 0.02 ms -2 ) AND part of (ii) with
correct force or distance with unit (m)
F = ma
OR
= 70 x 0.02 = 1.4 N (allow 1.46 if a unrounded)
Distance = area under graph or d = v (av) t
= 120 x 2.5
2 = 150m
For Excellence you require ALL answers correct with units (e)
W=Fd
F= ma = 70 x 0.02 = 1.4 N
d = area under graph or d = v (av) t
= 120 x 2.5
2 = 150m
(ii)
Calculate the work done by the cyclist in this time.
Additional Question over page
W = Fd = 1.4 x 150 = 210J