Physics Answers

An electric car is being driven through a town at 22 m/s. The kinetic energy of the car is 222640J. Calculate the mass of the car

You have been given a report analysing the stresses around a 40m by 4m rectangular excavation (stretching 100m in the out-of-plane dimension). The excavation was at a depth of 1800m and was modelled using a 2D plane strain finite element code. The model used a region of 320m horizontally by 60m vertically. The top and bottom boundaries were fixed in x and y displacements, while left and right boundaries were fixed in x displacement. The model used an in situ field-stress 20 MPa vertically and 10 MPa horizontally.

Sketch the above model clearly labelling relevant information. Discuss the accuracy of the model and the specific steps you would take to improve it. 

Show how the average energy in a Fermi gas can be expressed in terms of Ef0 

An elastic collision of two pucks (mA = 0.5 kg, mg = 0.3 kg) on a frictionless air-jockey table. Puck A has an initial velocity of 4m/s in the positive X-direction and a final velocity of 2m/s in an unknown direction a. Puck B is initially at rest. Find the final speed of puck B and the angles a and b.

Two rubber balls have an elastic head-on collision with each other. One ball has a mass of 0.25 kg and an initial velocity of 5.00 m/s. The other has a mass of 0.80 kg and is initially at rest. No external forces act on the ball. What are the velocities of the balls after the collision?

Aubrey drops a ball of mass 0.150 kg is dropped from rest from a height of 1.25 m. It rebounds from the floor to reach a height of 0.960 m. What impulse was given to the ball by the floor.

Differential between dynamics of system of particles and that of rigid

body.

A 2.2 kg block is attached to a spring that is attached to a vertical wall. The spring is stretched by 9 cm away from the wall and has a spring constant of 90 N/m. Assuming the mass of the spring is negligible, what is the magnitude and direction of the net force on the block? (Give the angle with respect to the horizontal, to the nearest degree.)

In the process of being felled, a tree is pushed horizontally to avoid hitting other trees as it falls. It feels a net force with a magnitude of 20,000 N as it falls. If the horizontal force on the tree is 2900 N, what is the weight of the tree?

A boat travels straight across a river with a net force of 150 N. If the boat is aimed 22° upstream, what is the magnitude of the force of the current?