Mechanics | Relativity Answers

The energy emitted by radiation by a blackbody of surface area 410m² and temperature of 155^•c

Block 1 of mass 𝑚1 = 2 𝑘g is placed on block 2 of mass 𝑚2 = 3 𝑘g which is then placed on a table. A string connecting block 2 to a hanging mass 𝑀 passes over a pulley attached to one end of the table, as shown in Fig. 1. The mass and friction of the pulley are negligible. The coefficients of friction between block 1 and block 2 are 𝜇_1s = 0.2, 𝜇_1k = 0.1 and between block 2 and the tabletop are 𝜇_2s = 0.3, 𝜇_2k = 0.15

(a) (Marks: 3) Draw the complete free body diagram of the system and determine the largest value of 𝑀 for which the blocks can remain at rest.

(b) (Marks: 4) Now suppose that 𝑀 = 2.5 𝑘g which is large enough so that the hanging block descends and block 1 slips on block 2. Draw the complete free body diagram of the system and determine each of the followings.

i. The magnitude 𝑎1of the acceleration of block 1.

ii. The magnitude 𝑎2 of the acceleration of block 2.

1.     A car starts from rest and attains a speed of 40 m/s in 20 s. its average acceleration in m/s² is

Block 1 and block 2, with masses m1 = 5 kg and m2 = 2 kg, are connected by a system of

massless, inextensible ropes and massless pulleys as shown in Fig. 2.

(a) (Marks: 2) Draw the complete free body force diagram of

the system.

(b) (Marks: 4) Solve for the accelerations of block 2 and block

1. Assume that downward direction is positive.

(c) (Marks: 2) Calculate the tensions in each rope.

A reservoir of glycerin has a mass of 1200 kg and a volume of 0.952 m3

. Find the

glycerin’s weight (W), density (𝜌), specific weight (𝛾), and specific gravity (SG).

A wet socks clinging to the inside of a washing machine drum which is spinning at a speed of 4.7 m/s. The radius of the drum is 30 cm.

(a) As the drum slows down after the washing is done at an angular retardation of 3.25 rad/sec^2 Find the time taken and number of rotations before it stops.

The acceleration of a point is a= 20t m/s2. When t= 0, x= 40 m and v= - 10 m/s. What are the position and velocity at t= 3 s?

The position of a point is given as a function of time by x= 4t − 6t + 2t− 1 , where x and t are expressed in meters and seconds. Determine the position, the velocity, and the acceleration of the particle when t= 2 s.

The coefficient of static and kinetic frictions between a 3.0-kg box and a desk are 0.40 and 0.30, respectively. What is the net force on the box when a 14.3 N horizontal force is applied to the box?

A 19.8 kg block is dragged over a rough, hor izontal surface by a constant force of 174 N acting at an angle of 25.8° above the horizon tal . The block is displaced 63.9 m, and the coefficient of kinetic friction is 0.123 .