Forces and Stopping Distance

IGCSE Edexcel Physics
1.15-1.21 Resultant Force, Friction, Stopping Distance
Key Concepts: Resultant force determines acceleration. Stopping distance = thinking distance + braking distance.

Section A: Resultant Force

1. A 700 N force acts forward and a 250 N force acts backward. Calculate the resultant force. [2]
2. A 15 kg trolley accelerates at $1.2\,m/s^2$. Calculate the resultant force. [2]

Section B: Stopping Distance

3. State the equation for stopping distance. [2]
4. Give three factors that increase stopping distance. [3]

Section C: Terminal Velocity

5. Explain how terminal velocity is reached for a falling object. [3]
6. A car slows uniformly from $20\,m/s$ to rest in 4.0 s. Calculate the braking distance. [3]
Total marks: 15

Mark Scheme

1. $700 - 250 = 450\,N$ forward [2]
2. $F = ma = 15 \times 1.2 = 18\,N$ [2]
3. Stopping distance = thinking distance + braking distance [2]
4. Any three: speed, mass, road condition, reaction time, tyre/brake condition [3]
5. Air resistance increases until it equals weight; resultant force becomes zero so speed is constant [3]
6. Distance = area under $v$-$t$: $\tfrac{1}{2} \times 20 \times 4 = 40\,m$ [3]