Question

1 fig. 2.1 shows a dummy of mass 70 kg used in a crash test to investigate the safety of a new car. the car approaches a solid barrier at 20 m/s. it crashes into the barrier and stops suddenly. (a) (i) calculate the momentum of the dummy immediately before the crash. momentum = ………………………………………… 2 (ii) determine the impulse that must be applied to the dummy to bring it to rest. impulse = ………………………………………… 1

Explanation:

Step1: Calculate the momentum before the crash

Momentum formula: \(p = mv\). Given \(m = 70\space kg\), \(v=20\space m/s\).
\(p=70\times20\)

Step2: Determine the impulse

Impulse - momentum theorem: \(J=\Delta p\). Initial momentum \(p_i = 1400\space kg\cdot m/s\), final momentum \(p_f = 0\space kg\cdot m/s\).
\(J=p_f - p_i=0 - 1400\)

Answer:

(i) \(1400\space kg\cdot m/s\)
(ii) \(- 1400\space N\cdot s\)