7.a railway truck A of a mass of 2000kg moves westwards with a velocity of 3m/s. It collides with a stationary truck B 1200kg, loaded with electronic equipment of mass 300kg. The two trucks combined after collision. Ignore the effects of friction. 7.1. Write down magnitude and direction of the 'reaction force' to the weight of truck A.
(2)
7.2. Calculate the velocity of truck B after the collision.
(5)
7.3. Calculate the magnitude of the force that the truck A exert on truck B if
the collision lasts for 0,5 s.
(4)
8. The most common reasons for rear-end collisions are too shortfollowing a
distance, speeding and failing brakes. The sketch below represents one such​

Acar travels along a highway with a velocity of 24 m/s, west. the car exits the highway; and 4.0 s later, its instantaneous velocity is 16 m/s, 45° north of west. what is the magnitude of the average acceleration of the car during the four-second interval?

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.

Henry, whose mass is 95 kg, stands on a bathroom scale in an elevator. the scale reads 830 n for the first 2.4 s after the elevator starts moving, then 930 n for the next 2.4 s. part a what is the elevator's speed 4.8 s after starting? express your answer with the appropriate units.