UNIVERSITY OF SOUTH AUSTRALIA SCHOOL OF PHYSICS & ELECTRONIC SYSTEMS ENGINEERING APPLIED PHYSICS 1 / PHYSICS 1S QUIZ 1 Time: 20 minutes
Marks: 15 Name ..................................................................................................... QUESTION (1 mark per question)
1.
A baseball player throws a ball vertically upward and catches it in the same spot when it returns to his mitt. At what point in the ball’s path does it experience zero velocity and non– zero acceleration at the same time? (A) Midway on the way up. (B) At the top of its trajectory. (C) The instant it leaves the catcher’s hand. (D) The instant before it arrives in the catcher’s mitt.
2.
If an object is thrown downward (rather than released from rest) its downward acceleration after release (in the absence of air resistance) is (A) (B) (C)
less than 9.8 m/s2, 9.8 m/s2,
greater than 9.8 m/s2.
3.
A ball is launched horizontally inside a large vacuum chamber in a laboratory. The ball’s horizontal component of velocity remains constant because (A) it is not acted upon by any forces, (B) it is not acted upon by any horizontal forces, (C) its initial vertical velocity was zero, (D) the net force on it is zero.
4.
An object weighing 200 N hangs motionless from a string attached to the ceiling. The net force acting on the object is (A) zero, (B) 20 N, (C) 200 N, (D) 2000 N.
5.
An object is given a push and it moves along a horizontal surface. What is the effect of the force of friction as the object moves? (A) It does positive work on the object. (B) It increased the object’s kinetic energy. (C) It increases the object’s potential energy. (D) Neither of the above.
ANSWER
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Problem 1 (3 marks) You are on a ledge in the dark and wish to estimate the height of the ledge above the ground. You drop a stone over the edge and hear it strike the ground 1 s later. What is the height of the ledge? How could you use the stone to estimate the height of the ledge if you were not close enough to the edge to simply drop the stone? Explain. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. .................................................................................................................................................................................
Problem 2 (3 marks) A 7.00 kg bowling ball moves at 3.00 m/s. How fast must a 46 g golf ball move so that the two balls have the same kinetic energy? ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. .................................................................................................................................................................................
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Question (4 marks) Briefly describe the forces acting on a person standing on a horizontal surface and identify the ‘reaction’ force corresponding to each. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. ................................................................................................................................................................................. .................................................................................................................................................................................