Midterm Examination, Physics 1P21

Transcription

1 Midterm Examination, Physics 1P21 Prof. S. Bose Feb. 25, 2015 Last Name First Name Student ID Circle your course number above No examination aids other than those specified on this examination script are permitted (FHB A). Use or possession of unauthorized materials will automatically result in the award of a zero grade for this examination. This is a closed book test, calculators are allowed Formula sheet supplied with the exam can be used. No other aid is allowed. Attempt all questions Question Mark Out of 1 a b c d e 2 2 a b c d e 2 3 a b c d e 2 4 a b c d e 2 5 a b c d e Total 42 1

2 Physics 1P21 Midterm, Feb. 25, 2015 page 2 This exam contains 7 pages as well as an equation sheet. Please, verify that your copy is complete.

3 Physics 1P21 Midterm, Feb. 25, 2015 page 3 For questions 1 5: circle the correct answer on the front page. (2) 1. The velocity of a train is 80.0 km/h, due west. One and a half hours later its velocity is 65.0 km/h, due west. What is the train s average acceleration? (a) 43.3 km/h 2, due west (b) 53.3 km/h 2, due east (c) 10.0 km/h 2, due west (d) 43.3 km/h 2, due east (e) 10.0 km/h 2, due east (2) 2. Ball 1 is thrown into the air and it follows the trajectory for projectile motion shown in the drawing. At theinstant itisatthetopofitstrajectory, Ball2isdroppedfromrest atthesame height. Just before they reach the ground, the velocity of Ball 1 has a horizontal component v x and a vertical component v y. Ball 2 only has a vertical component. Which ball has the greater vertical component? (a) Both balls have the same vertical component. (b) Ball 2 has the greater vertical component. (c) There is not enough information to tell which ball has the greater vertical component. (d) Ball 1 has the greater vertical component. (e) The answer depends on the horizontal velocity of ball 1. (2) 3. When the net force that acts on a hockey puck is 12 N, the puck accelerates at a rate of 48 m/s 2. The mass of the puck is (a) 5.0 kg (b) 2.5 kg (c) 2.0 kg (d) 0.25 kg (e) 1.0 kg (2) 4. Dave pushes his four-year-oldson Thomas across the snow onasled. As Davepushes, Thomas speeds up. Which statement is true? (a) The force of Dave on Thomas is larger than the force of Thomas on Dave. (b) The force of Thomas on Dave is larger than the force of Dave on Thomas. (c) Both forces have the same magnitude. (d) It depends on how hard Dave pushes on Thomas.

4 Physics 1P21 Midterm, Feb. 25, 2015 page 4 (2) 5. A boy is whirling a stone around his head by means of a string nearly parallel to the ground. The string makes one complete revolution every second and the tension in the string is F T. The boy then speeds up the stone, keeping the radius of the circle unchanged, so that the string makes two complete revolutions every second. What happens to the tension in the string? (a) The tension is unchanged. (b) The tension reduces to one-fourth of its original value. (c) The tension reduces to half of its original value. (d) The tension increases to twice its original value. (e) The tension increases to four times its original value.

5 Physics 1P21 Midterm, Feb. 25, 2015 page 5 (10) 6. A horizontal rifle is fired at a bull s-eye. The muzzle speed of the bullet is 650 m/s. The gun is pointed directly at the center of the bull s-eye, but the bullet strikes the target m below the center. What is the horizontal distance between the end of the rifle and the bull s-eye?

6 Physics 1P21 Midterm, Feb. 25, 2015 page 6 (15) 7. A gardener mows a lawn with an old-fashioned push mower. The handle of the mower makes an angle of 32 with the surface of the lawn. If the gardener pushed down with a 209 N force along the handle of the 18 kg mower, what is the normal force exerted by the lawn on the mower? If the gardender pulls the mower along the direction of the handle, instead of pushing it, will the normal force be greater than, less than or the same magnitude as the weight? Explain.

7 Physics 1P21 Midterm, Feb. 25, 2015 page 7 (10) 8. The turns at the Daytona International Speedway have a maximum radius of 316 m and are steeply banked at 31 degrees. Suppose these turns were frictionless. At what speed would the cars have to travel around them in order to remain on the track?