2 (b) A car of mass 850kg tows a trailer in a straight line along a horizontal road, as shown in [Figure 2.1]. The car and the trailer are connected by a horizontal tow-bar. The variation with time t of the velocity v of the car for a part of its journey is shown in [Figure 2.2].

1. (a)State Newton's second law of motion.[1]
2. (b)(i)Calculate the distance travelled by the car from time t = 0 to t = 10s.[2]
3. (b)(ii) 1.use Fig. 2.2 to calculate the acceleration[2]
4. (b)(ii) 2.use your answer to calculate the resultant force acting on the car[1]
5. (b)(ii) 3.show that a horizontal force of 1300N is exerted on the car by its engine[1]
6. (b)(ii) 4.determine the useful output power of the engine.[2]
7. (c)A short time later, the car in (b) is travelling at a constant speed and the tension in the tow-bar is 480 N. The tow-bar is a solid metal rod that obeys Hooke's law. Some data for the tow-bar are listed below. Young modulus of metal = 2.2 × 10¹¹ Pa original length of tow-bar = 0.48 m cross-sectional area of tow-bar = 3.0 × 10⁻⁴ m² Determine the extension of the tow-bar.[3]
8. (d)The driver of the car in (b) sees a pedestrian standing directly ahead in the distance. The driver operates the horn of the car from time t = 15s to t = 17s. The frequency of the sound heard by the pedestrian is 480 Hz. The speed of the sound in the air is 340ms⁻¹. Use Fig. 2.2 to calculate the frequency of the sound emitted by the horn.[2]

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