Mechanical Engineering Answers

A scooter has hydraulic disc brakes both front and rear. The brakes have a brake piston on each side of the disc. The average radius of the blocks' contact with the disc is 10 cm, the piston diameter is 20 mm and the steel disc weighs 0.8 kg. The coefficient of friction between the coating and the disc is assumed to be 0.4. The scooter weighs 160 kg including the driver and the weight distribution is 50% front and 50% rear regardless of whether you brake or not. The wheelbase (the distance between the center of the front and rear wheels) is 1.37 m and the wheel diameter is 0.45 m. Assume that you only brake with the front wheel and that the friction number between the tire and the road surface is 0.9. Steel has a specific heat capacity of 450 J / (kg ° C).

1. What is the minimum possible braking distance (you brake so hard that the front wheel is on the verge of locking) when braking from 50 km / h to a standstill?

A scooter has hydraulic disc brakes both front and rear. The brakes have a brake piston on each side of the disc. The average radius of the blocks' contact with the disc is 10 cm, the piston diameter is 20 mm and the steel disc weighs 0.8 kg. The coefficient of friction between the coating and the disc is assumed to be 0.4. The scooter weighs 160 kg including the driver and the weight distribution is 50% front and 50% rear regardless of whether you brake or not. The wheelbase (the distance between the center of the front and rear wheels) is 1.37 m and the wheel diameter is 0.45 m. Assume that you only brake with the front wheel and that the friction number between the tire and the road surface is 0.9. Steel has a specific heat capacity of 450 J / (kg ° C).

1. Which is the largest braking force that can be transmitted between the front wheel and the ground?

in a three-wheel planetary gear, the sun gear has 19 teeth and the planet wheels 17 teeth each. The teeth are not profiled. The energy is fed in via the sun wheel and taken out via the planetary bar. The load must be driven with a power of 1,000 W and rotated at a speed of 1,200 rpm. The efficiency between sun gear and planet gear is assumed to be 0.98 and between planet gear and ring gear to 0.96

1. How many teeth does the outer sun gear have?
2. What gear ratio does the gear have?
3. What is the efficiency of the gear unit??
4. What speed should the engine rotate with?
5. What torque must the engine deliver?

In a slider crank mechanism the length of the crank OB is (174)mm and length of the connecting rod is (549)mm. The center of gravity G of the connecting rod is (324)mm from the slider A. crank speed is (574)rpm clockwise. When the crank has turned 45 deg. From the inner dead center

. Determine (using both relative velocity method and Instantaneous center method)

1. Velocity of the slider

2. Velocity of point G

3. Angular velocity of the connecting rod AB

The wall of a house consists of two 125mm brick walls with an inner cavity. The inside wall has a 10mm coating of plaster and there is a cement rendering of 5mm on the outside wall. In one room of the house the external wall is 4m by 2.5m

Determine the member forces and the reaction forces for the truss structure shown in figure with proper assumptions

A member ABCD is subjected to point loads P1, P2, P3 and P4 as shown in Fig. Calculate the force P3,necessary for equilibrium if P1 = 120 kN, P2 = 220 kN and P4 = 160 kN. Determine also the net change in length of the member. Take E = 200 GN/m2.

Direct stresses of 120 N / mm ^{2}N/mm2 (tension) and 90 N / mm ^{2}N/mm2 (compression) are applied at a particular point in an elastic material on two mutually perpendicular planes. The principal stress in the material is limited to 100 N / mm ^{2}N/mm2 (tension). Calculate the allowable value of shear stress at the point on the given planes. Determine also the value of the other principal stress and the maximum value of shear stress at the point. Verify your answer using Mohr’s circle.

A triaxial stress element as shown in Figure has σx = 40 MPa, σy = –20 MPa, σz = –10 MPa, τxy = 5 MPa, τyx = –1.5 MPa, τzx = 2.5 MPa. Answer following questions:

Find the principal stresses using a numerical method (i.e., using Eigen values method) and draw the resulting Mohr’s circles. (You can use Scientific Calculator for calculating eigen values of the stress matrix)

Draw the resulting Mohr's circles.

A high strength steel of yield strength: 1200 Mpa in form of wide plate contains a Semi elliptical surface crack of depth 10mm and length 100mm and located at centre of plate. The plate is subjected to tensile stress at 90° angle to crack. The plate was found to break in service in unstable manner resulting completely flat fracture surface. the size of plastic zone measured at minor crack tip just at the instant of fracture to be 0.25 mm. what could be have the fracture toughness