### SEB101 – Engineering Physics

__SEB101 – Engineering Physics__

T1 2021 Mid-Trimester Assignment

**Instructions:**

Answer ALL 10 questions on paper, clearly showing your working. When done, scan your work to a .PDF file and submit it to the submission folder on the SEB101 unit site. Each question is worth 10 marks.

__Due date: 30 April, 2021, 8:00 PM Melbourne time.__

This assignment is worth 10% of your grade in this unit.

1. Someone sees a ball that sails first up and then down past an open window. The ball is in view for a total of 0.50 seconds. The height of the window top-to-bottom is 2.00 m. How high above the top of the window does the ball go?

2. Vector **A** lies in the xy plane 30.0 degrees anti-clockwise from the +x axis, and has magnitude 5.0 m.

Vector **B** lies in the xy plane 45 degrees clockwise from the +x axis, and has magnitude 4.0 m.

a. Determine A●B.

b. In unit vector notation, determine A×B.

c. What is the magnitude of the cross product?

d. What angle does the cross product make with the +y axis?

3. A projectile is launched horizontally from a height h of 40 m above level ground with an initial speed v0. When it lands, the inclination angle θis 70 degrees from the horizontal. In unit-vector notation, determine the initial velocity of the object.

4. The figure shows two blocks connected by a massless rope that passes over a frictionless pulley.

Mass m1 = 1.30 kg; mass m2 = 2.80 kg.

a. Determine the magnitude of the blocks’ acceleration.

b. Determine the tension in the rope.

5. In the figure below, two blocks are connected by a rope over a pulley. Angle θ of the incline is 30°. The mass of block A is 10 kg. The coefficient of kinetic friction between mass A and the incline is 0.20. Block A slides down the incline with constant speed.

Determine the mass of block B. Assume that the mass of the connecting rope is 0.

6. The cab of a goods lift has a total mass of 1200 kg. It is required to travel upward 54 m in 3.0 min, starting and ending at rest. The lift’s counterweight has a mass of 950 kg. A motor must help with the lifting. What average power is required of the force the motor exerts on the cab by means of the cable?

7. On a frictionless incline with incline angle θ = 30.0°, a block with mass m = 2.00 kg is placed against a spring (shown below).

The spring constant k = 1960 N/m. The spring is compressed 200 mm and then released. (The block is not attached to the spring.)

a. Determine the elastic potential energy of the compressed spring.

b. Determine the change in the gravitational potential energy of the block–Earth system as the block moves from the release point to its highest point on the incline.

c. How far along the incline is the block’s highest point from the release point?

8. A thin hollow ball has a radius of 1.90 m. About an axis through the centre of the ball, an applied torque of 960 N?m gives it an angular acceleration of 6.20 rad/s2 . Determine:

a. the rotational inertia of the ball about that axis and

b. the mass of the ball.

9. An applied force N is applied to an object at position . Determine the moment of this force about the origin.

10. In the figure below, the length L of the uniform bar is 3.00 m and its weight is 200 N. The weight of the block is W = 300 N. The angle θ = 30.0°. The wire fails when the tension reaches 500 N.

a. Determine the maximum possible distance x before the wire breaks. With the block placed at this maximum x, what are the

b. horizontal and

c. vertical components of the force on the bar from the hinge at point A?

2021-04-26