Example 9.13 A car of mass 1000 kg travelling at \( 36 \mathrm{~km} / \mathrm{h} \) is brought to rest by applying brakes. Calculate the distance travelled by the car before coming to rest, if the frictional force between the twheels and the road is 2000 N . Solution

A bullet of mass 120 grams is fired into a target of mass 10 kg with velocity \( 400 \mathrm{~m} / \mathrm{s} \). If the target is free to move, the loss of kinetic energy would be approximately \( \begin{array}{ll}\text { (1) } 9.5 \mathrm{kNm} & \text { (2) } 4.75 \mathrm{kNm} \\ \text { (3) } 19 \mathrm{kNm} & \text { (4) } 0\end{array} \)

4. В закрытом баллоне вместимостью 20 л находится арг под давлением 200 кПа. Газ передал окружающей среде 120 Дж количества теплоты, и его температура понизилась ло 200 K . Определите начальную температуру аргона.

2. एक ही दिशा में चल रहे दो रेल इंजन जिनका वज़न 120 kN व 100 kN हैं, टकराने के पश्चात् एक साथ आगे बढ़ते हैं । टक्कर के पश्चात् समान गति (speed) होगी \( \begin{array}{ll}\text { (1) } 3.8 \mathrm{~m} / \mathrm{s} & \text { (2) } 3.9 \mathrm{~m} / \mathrm{s} \\ \text { (3) } 4.0 \mathrm{~m} / \mathrm{s} & \text { (4) } 4.1 \mathrm{~m} / \mathrm{s}\end{array} \)

14 If velocity, momentum and kinetic energy of a particle are represented by \( v, p \) and \( k \) respectively then, which relation is correct ? \( \begin{array}{ll}\text { (1) } p=\frac{d k}{d v} & \text { (2) } p=\frac{d k}{d t} \\ \text { (3) } p=\frac{d v}{d t} & \text { (4) } p=\left(\frac{d k}{d v}\right)\left(\frac{d k}{d t}\right) \\ \text { यदि } \nu, p \text { और } k \text { क्रमशः कण के वेग, संवेग और गतिज ऊर्जा हैं तो निम्न में से } \\ \text { कौन-सा सम्बन्ध सही है ? } \\ \begin{array}{ll}\text { (1) } p=\frac{d k}{d v} & \text { (2) } p=\frac{d k}{d t}\end{array}\end{array} \).

? (What is free fall?) (What is gravity?)