Cyclist and delivery van

Question 1

(a) $a=15/3.0$ or $(v-u)/t$ [1]; $5.0\,\text{m/s}^2$ [1]

(b) Split [1]; $\tfrac{1}{2}\times 3.0\times 15=22.5\,\text{m}$ [1]; $6.0\times 15=90\,\text{m}$ [1]; last triangle $22.5\,\text{m}$, total $135\,\text{m}$ [1]

Question 2

(a) $5400-1800$ [1]; $3600\,\text{N}$ [1]

(b) $3600/1800$ [1]; $2.0\,\text{m/s}^2$ [1]

(c)(i) Acceleration decreases because mass increases and $F$ is unchanged / $a=F/m$ [1]

(c)(ii) Stopping distance $= 9.0+24=33\,\text{m}$ [1]; extra mass increases braking distance (same braking force gives smaller deceleration) [1]. Allow 1 for $33\,\text{m}$ and 1 for the mass/braking explanation if they omit the add.

Question 3

(a) Constant / maximum speed [1]; when air resistance equals weight / resultant is zero [1]

(b) Any four: parachute increases area so air resistance suddenly larger than weight [1]; resultant force upwards / she decelerates [1]; as speed falls, air resistance falls [1]; until $R=W$ again [1]; new (smaller) terminal velocity [1]

Question 4

(a) Mass in kg (e.g. $0.100\,\text{kg}$) [1]; $W=mg$ so $0.100\times 10=1.0\,\text{N}$ per $100\,\text{g}$ (or equivalent) [1]

(b)(i) Uses a linear pair, e.g. $4.5\,\text{N}$ and $0.060\,\text{m}$ [1]; $k=75\,\text{N/m}$ [1]. Also accept $1.5/0.020$ or $3.0/0.040$.

(b)(ii) No [1]; extension step is larger than $2.0\,\text{cm}$ / not proportional / past limit of proportionality [1]