Engineering Answers

A motor car, of total mass 1400kg, running in top gear at 55km/h, passes on to a rising of 1 in

20 at that speed. The road and other resistances may be taken as constant at 270N/t. With

conditions unchanged, the speed falls uniformly to 40km/h in a distance of 360m. An

intermediate gear is then engaged for which the speed ratio between the engine and the road

wheels is 9:1 and the transmission efficiency is 85%. The engine is then developing a torque

of 85Nm. Determine: (a) The tractive efforts before and after the gear change, given that the

road wheels are 750mm in diameter, (b) The time between the start of retardation and the

recovery of the original speed of 55km/h, and (c) The powers being developed by the engine

when the car is retarding and accelerating through 50km/h, given that the transmission

efficiency in top gear is 94%.

(b) the current flowing in each of the four resistors . R1=15ohms, R2=10ohms, R3=38ohms and R4=Rx.

The current i (in amps) t seconds after closing the switch in the circuit shown is given by: i(t) = V/R(1-e-(R/L)t) Consider the case where V = 120 volts, R = 120 Ohms and L = 0. 1 henry. Find the time tm required for the current to reach 99% of its final value, then use linspace to create a vector t having 10 elements with the first element 0 and maximum value tm. Calculate the current i for each value of t from part (a). The length |u| (magnitude) of a vector u = given by |u| = x2+y2+z2. Given the vector u = 23. 5i - 17j + 6k, determine its length two ways:

State a laplace transform function and explain the meaning

1. Ring the alarm on time 2. Make coffee 3. Heat the water to a suitable temperature 4. Pack your bag 5. Cook breakfast and lunch 6.iron the clothes