Mechanics | Relativity Answers

i and j are unit vectors along x and y axis respectively. What is the magnitude and direction of the vectors i + j, and i − j ? What are the components of a vector A= 2i + 3j along the directions of i + j and i − j? [You may use graphical method]

an air bubble has a volume of 2cm^3 when released at a depth of 20min water. what will its volume be when it reaches the surface. assume that the temperature does not change and that atmospheric pressure is equivalent to the atmospheric pressure from a column of water 10m deep

A fisherman has caught a very large, 5.0 kg fish from a dock that is 2.0 m above the water. He is using lightweight fishing line that will break under a tension of 54 N or more. He is eager to get the fish to the dock in the shortest possible time.
If the fish is at rest at the water's surface, what's the least amount of time in which the fisherman can raise the fish to the dock without losing it?

A fisherman in a boat catches a huge fish with a rod and starts to pull it in. The fish struggles for a while and then becomes still when it is at a distance of 200m from the boat. During this operation,the boat(initially at rest)moves 25 m in the direction of the fish.If the mass of the boat is 5000kg, calculate the mass of the fish.Assume that water experts no friction.

Two forces on the object are F1 = 3.6 N at 74° below the +x-axis and F2 = 3.6 N at 34° above the -x-axis. Is there a third force on the object, and why?

If yes, what is it? (If there is none, specify zero magnitude and direction.)
magnitude
N direction
° (counterclockwise from the +x-axis)

Use gravitational force as 10n,weight is measured in n and mass is measured in kg.acceleration at 30ms negative square 1000kg=1 ton 1000mg=1kg
1.a loaded truck weighing 35 tonnes was accelerating at 30ms negative square and hit a stable rock. Calculate the force on the rock.

A 5.00-kg object is moving at a constant speed of 8.00 m/s on a horizontal surface. What is the kinetic energy of the car?

19 The predominant mode of heat transfer in solids is -----------
convection
conduction
radiation
diffusion

20 A piece of plastic barely floats in water. If it has a mass of 20g, what is its volume?
30cm3
20cm3
10cm3
2cm3

11 Calculate the electric power which must be supplied to the filament of of a light bulb operating at 3000K. The total surface area of the filament is
8×10−6m2
and its emissivity is 0.92.
20.3W
33.8W
46.4W
56.7W

12 Calculate the change in internal energy of 2kg of water at
90oC
when it is changed to
3.30m3
of steam at
100oC
. The whole process occurs at atmospheric pressure. The latent heat of vaporization of water is
2.26×106J/kg
.
4.27 MJ
3.43 kJ
45.72 mJ
543.63 J

12 A string of natural length L extends to a new length L' under tensile force F. If Hooke’S law applies, the work done in stretching the spring is ------------
1/2FL
1/2FL'
1/2 F(L-L')
F(L-L')

13 The molecules of a liquid are held together by what type of forces?
cohesive forces
adhesive forces
viscosity
surface tension forces

14 Which of these is correct about viscosity?
it increases with increase in temperature
it varies with the relative velocity of the surfaces in contact
it is does not vary from one liquid to another
both viscous force and upthrust act upwards