Discussion Class 1
Questions
Q2)The diagram shows an overhead view of four particles of equal mass sliding over a frictionless surface with constant velocity. The directions of the velocities are as indicated, the magnitudes are equal. Consider pairing the particles.
Which particles when paired will result in a centre of mass that is:
a)Stationary
A and C, C and B
b)Stationary and at the origin
C and B
c)Moving and passes through the origin at some stage
B and D, A and D
Problems
P2) AA three particle system, with masses , and is depicted in the diagram alongside where the axes scales are set by . Find the coordinates of the centre of mass of the system.
P3)The diagram below shows a composite slab constructed from equal volumes of iron (density = ) and aluminium (density = ). The dimensions of the slab are and . Find the coordinates of the centre of mass of the slab
Iron / / / /aluminium / / / /
P6) A cubical box that has been constructed from uniform plates of negligible thickness. The box is open at the top and has edge length . Find the coordinates of the centre of mass of the box
Side / / / /Discussion Class 2
Questions
Q7)A block slides along a frictionless floor and into a stationary second block with the same mass. The diagram below shows four choices for a of graph of the kinetic energy of the blocks as a function of time.
a)Which of these graphs represent physically impossible situations and why?
C. Kinetic energy can never be negative
D. Total kinetic energy can never increase
b)Of the others, which best represents an elastic and an inelastic collision?
Elastic = A (total kinetic energy is conserved)
Inelastic = B (total kinetic energy has decreased)
Problems
P38) A 300 g ball with a speed of 8.0 m/s strikes a wall at an angle of 30° and then rebounds with the same speed and angle. It is in contact with the wall for 10 ms. In unit vector notation what is:
a)The impulse on the ball from the wall
(Note answer may vary in terms of sign or component if diagram drawn differently but magnitude will be invariant)
b)The average force on the wall from the ball
P44) A stationary block explodes into two pieces L and R that slide across a frictionless floor and then into regions with friction, where they are slowed to a stop. Piece L, with a mass of 2.0 kg, encounters a coefficient of kinetic friction and slides to a stop in distance . Piece R encounters a coefficient of kinetic friction and slides to a stop in distance . What was the mass of the block?
P68)Block 1 of mass slides from rest along a frictionless ramp from height and then collides with stationary block 2, which has mass . After the collision, block 2 slides into a region where the coefficient of kinetic friction is 0.450 and comes to a stop in distance d within that region.
a)What is the value of d if the collision is elastic?
Elastic collision:
Conservation of linear momentum:
b)What is the value of d if the blocks stick together after the collision?
Conservation of linear momentum: