Question

A 2500-kg truck traveling at 40 km/h strikes a brick wall and comes to a stop in 0.2 s. (a)
What is the change in momentum? (b) What is the impulse? (c) What is the average
force on the wall during the crash?

Answer 1

Answer on Question #74640, Physics Mechanics Relativity

A 2500-kg truck traveling at 40 km/h strikes a brick wall and comes to a stop in 0.2 s.

(a) What is the change in momentum?

**Solution.**

$$J = F \cdot \Delta t = m V - m V _ {0}$$ $$J = 2 5 0 0 \cdot (0 - 4 0) = - 1 0 0 0 0 0 \mathrm {k g} \cdot \mathrm {m} / \mathrm {s} (\mathrm {N} \cdot \mathrm {s})$$

Answer: $J = -100000 \, \mathrm{kg} \cdot \mathrm{m/s} \, (\mathrm{N} \cdot \mathrm{s})$

(b) What is the impulse?

Answer: Impulse is a term that quantifies the overall effect of a force acting over time. It is conventionally given the symbol $J$ and expressed in Newton-seconds.

For a constant force, $J = F \cdot \Delta t$

(c) What is the average force on the wall during the crash?

**Solution.**

$$F _ {a v} = \frac {(m V - m V _ {0})}{\Delta t}$$ $$F _ {a v} = \frac {(2 5 0 0 \cdot 0 - 2 5 0 0 \cdot 4 0)}{0 . 2} = - 5 0 0 0 0 0 N \cdot s$$

Answer: $F_{\mathrm{av}} = -500000 \, \mathrm{N} \cdot \mathrm{s}$

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