UNIVERSITY OF SOUTH AUSTRALIA SCHOOL OF PHYSICS & ELECTRONIC SYSTEMS ENGINEERING APPLIED PHYSICS 1 / PHYSICS 1S QUIZ 2 Time: 20 minutes
Marks: 15 Name ..................................................................................................... QUESTION (1 mark per question)
1.
A karate expert executes a swift blow and breaks a cement block with a bare hand. The magnitude is the same for the (A) impulse on both the block and the expert’s hand, (B) force on both the block and the expert’s hand, (C) time of impact on both the block and the expert’s hand, (D) all of these.
2.
If the polar ice caps melted, the resulting water would spread over the entire earth. This new mass distribution would tend to make the length of a day (A) longer, (B) shorter, (C) stay the same.
3.
Consider a point on a bicycle wheel as the wheel turns about a fixed axis, neither speeding up nor slowing down. Compare the linear and angular accelerations of the point. (A) Both are zero. (B) Only the angular acceleration is zero. (C) Only the linear acceleration is zero. (D) Neither is zero.
4.
The total kinetic energy of a baseball thrown with a spinning motion is a function of which of the following? (A) Its linear velocity but not angular velocity. (B) Its angular velocity but not linear velocity. (C) Both linear and angular velocities. (D) Neither linear nor angular velocity.
5.
If the net external torque on a rigid body about some origin is zero, it means that (A) the angular momentum of the rigid body about the origin is constant, (B) the angular acceleration of the rigid body about the origin is zero, (C) the angular speed of the rigid body about the origin is constant, (D) all of the above are true.
ANSWER
– 2 –
PLEASE TURN OVER
Problem (7 marks) A disk 8.00 cm in radius and with a moment of inertia of 1.6 x 10–3 kg.m2 rotates at a constant rate of 1200 revolutions per minute about its central axis. Determine (a) its angular speed (1.5 marks), (b) the linear speed of a point on the rim of the disk (1 mark), (c) the magnitude and direction of the linear acceleration of a point on the rim (1 + 0.5 marks), (d) the angular momentum of the disk (1.5 marks), and (e) the kinetic energy of the disk (1.5 marks). ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. .................................................................................................................................................................................
Question (3 marks) State the impulsemomentum theorem and use it to explain why it is preferable for a car passenger’s head to hit an inflated airbag rather than the dashboard. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. .................................................................................................................................................................................