Investigating Forces & Motion

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INI File | 1998-02-10 | 11KB | 349 lines

[question1] type:2 caption:\ A footballer shoots 15 m from the goal. If the ball travels at an \ average speed of 30 m/s, how long does the goalkeeper have to make a \ save? correct:0.5 s wrong1:2.0 s wrong2:1.0 s wrong3:0.1 s feedback:\ <img src="sa1q1a" align=center>\ so,\ <img src="sa1q1b" align=center>\ <img src="sa1q1c" align=center>\ <center>= 0.5 s.</center> [question2] type:2 caption:\ A drag-racing car takes 6.0 s to cover a 400 m course from a standing \ start. If the car is travelling at 132 m/s as it crosses the finish \ line, what is its average acceleration for the whole race? correct:22 m/s2 wrong1:132 m/s2 wrong2:67 m/s2 wrong3:30 m/s2 feedback:\ <img src="sa1q2a" align=center>\ <img src="sa1q2b" align=center>\ <center>= 22 m/s2.</center> [question3] type:1 image:1g10 caption:\ A person carrying a dripping bucket walks across a floor covered with \ 1.0 m square tiles. You can see the pattern left by the drips. If the \ bucket was dripping at a constant rate of two drips per second, how \ fast was the person walking? correct:1.5 m/s wrong1:0.5 m/s wrong2:1.0 m/s wrong3:3.0 m/s feedback:\ Two drips per second means that the time interval between drips is 0.5 \ s. The distance between drips is 0.75 m, therefore,\ <img src="sa1q1a" align=center>\ <img src="sa1q3a" align=center>\ <center>= 1.5 m/s.</center> [question4] type:1 image:1g11 caption:\ This series of photographs shows a rabbit accelerating from a standing \ start against a background grid. If the photographs were recorded at \ 0.5 s intervals, what was the rabbit's acceleration? correct:4.0 m/s2 wrong1:1.0 m/s2 wrong2:2.0 m/s2 wrong3:3.0 m/s2 feedback:\ In the first 0.5 s interval, the rabbit travels 1.0 m. The rabbit's \ average speed is therefore <img src="sa1q4a" align=center>\ The rabbit travels 2.0 m in the next 0.5 s, so its average speed is \ therefore\ <img src="sa1q4b" align=center>\ <img src="sa1q2a" align=center>\ <img src="sa1q4c" align=center>\ <center>= 4.0 m/s2.</center> [question5] type:2 caption:\ A car makes a journey of 30 km in 20 minutes. What was its average \ speed in metres per second? correct:25 m/s wrong1:1.5 m/s wrong2:2.0 m/s wrong3:15 m/s feedback:\ To calculate the correct answer, you must first convert kilometres to \ metres and minutes to seconds:\ 30 km = 30 x 1 000 m\ 20 minutes = 20 x 60 s\ Then calculate the car's average speed using the following \ equation:\ <img src="sa1q5a" align=center>\ <img src="sa1q5b" align=center>\ <center>= 25 m/s.</center> [question6] type:2 caption:\ What is the average velocity of an athlete who completes one lap of a \ 400 m track and returns to the starting line in 50 s? correct:0.0 m/s wrong1:4.0 m/s wrong2:8.0 m/s wrong3:20 m/s feedback:\ <img src="sa1q6a" align=center>\ Velocity is a vector quantity; it can be negative as well as positive. \ As the track is circled, the athlete's velocity changes direction. On \ one side of the track it is positive, but on the other side it is \ negative, so the average velocity for a complete lap is 0.0 m/s.\ To put it another way, when the athlete returns to the starting point, \ displacement is 0.0 m. Using the above equation, we find that: <img \ src="sa1q6b" align=center> [question7] type:2 caption:\ What is the average speed of an athlete who completes one lap of a 400 \ m track and returns to the starting line in 50 s? correct:8.0 m/s wrong1:0.0 m/s wrong2:4.0 m/s wrong3:20 m/s feedback:\ Speed does not have a direction, so the athlete's speed is always \ positive. We can calculate the athlete's speed with the equation:\ <img src="sa1q1a" align=center>\ <img src="sa1q7a" align=center>\ <center>= 8.0 m/s.</center> [question8] type:2 caption:What are the units of acceleration? correct:m/s2 wrong1:ms2 wrong2:ms wrong3:m/s feedback:\ Acceleration is equal to the change in velocity divided by the time it \ takes for the change to occur. The units of velocity are metres per \ second (m/s), so the units of acceleration are metres per second per \ second, or m/s2. [question9] type:2 caption:\ A rocket is launched from rest with an acceleration of 5.0 \ m/s2. What is its speed after 10 seconds? correct:50 m/s wrong1:20 m/s wrong2:5.0 m/s wrong3:2.0 m/s feedback:\ Because the rocket is accelerating in a straight line, its speed \ change is the same as its velocity change.\ <img src="sa1q9a" align=center>\ so,\ velocity change = acceleration x time\ <center>= 5.0 x 10</center>\ <center>= 50 m/s.</center> [question10] type:1 image:1g12 caption:\ The tracks below are the fossilised footprints of a dinosaur running \ on its hind legs. Tests on this species' skeleton show that it could \ probably have taken one stride every 0.5 s. How fast was this dinosaur \ running? correct:10 m/s wrong1:2.0 m/s wrong2:5.0 m/s wrong3:20 m/s feedback:\ The distance between footprints is 5.0 m.\ <img src="sa1q1a" align=center>\ <img src="sa1q10a" align=center>\ <center>= 10 m/s.</center> [question11] type:2 caption:\ A rocket must reach a speed of 8 400 m/s to get into orbit around the \ Earth. If it is launched from rest and enters orbit 2.0 minutes later, \ what is its average acceleration? correct:70 m/s2 wrong1:2.0 m/s2 wrong2:8.4 m/s2 wrong3:4 200 m/s2 feedback:\ <img src="sa1q9a" align=center>\ <img src="sa1q11a" align=center>\ <center>= 70 m/s2.</center> [question12] type:1 image:1g13 caption:\ A child on a fishing boat is throwing fish heads over the side at the \ rate of one every 5.0 s. The pattern of splashes behind the boat is \ shown on the diagram. Which graph shows how the boat's velocity is \ changing? correct:Graph A wrong1:Graph B wrong2:Graph C wrong3:Graph D feedback:\ The splashes are getting closer together at a steady rate, showing \ that the boat is slowing down with a uniform negative acceleration. [question13] type:2 caption:\ A moving car starts accelerating along a straight road. During the \ first second it travels 20 m. During the next second it travels 24 m. \ What is the car's acceleration? correct:4.0 m/s2 wrong1:8.0 m/s2 wrong2:24 m/s2 wrong3:20 m/s2 feedback:\ <img src="sa1q1a" align=center>\ <img src="sa1q9a" align=center>\ The speed in the first second = <img src="sa1q13a"> = 20 m/s\ The speed in the second second = <img src="sa1q13b"> = 24 m/s\ Because the acceleration is in a straight line, the speed change \ equals the velocity change.\ <img src="sa1q13c" align=center> [question14] type:2 caption:\ A cyclist travelling at 10.0 m/s brakes sharply and comes to rest in \ 2.5 s. What is the cyclist's acceleration? correct:-4.0 m/s2 wrong1:4.0 m/s2 wrong2:7.5 m/s2 wrong3:-7.5 m/s2 feedback:\ <img src="sa1q9a" align=center>\ <img src="sa1q14a" align=center>\ <img src="sa1q14b" align=center>\ <center>= -4.0 m/s2.</center> [question15] type:1 image:1g14 caption:\ A ticker-tape timer makes one dot every 0.02 s. What is the speed of \ the truck that pulled this tape through the timer? correct:1.5 m/s wrong1:0.5 m/s wrong2:1.0 m/s wrong3:2.0 m/s feedback:\ The distance between consecutive dots is 3.0 cm.\ <img src="sa1q1a" align=center>\ <img src="sa1q15a" align=center>\ <center>= 150 cm/s = 1.5 m/s.</center> [question16] type:1 image:1g15 caption:\ A ticker-tape timer makes one dot every 0.02 s. What is the \ acceleration of the truck that pulled this tape through the timer? correct:12.5 m/s2 wrong1:2.5 m/s2 wrong2:5.0 m/s2 wrong3:25 m/s2 feedback:\ The distance between dots increases by 0.5 cm every 0.02 seconds. This \ means that the velocity increases by 0.5 ÷ 0.02 = 25 cm/s every \ 0.02 s.\ <img src="sa1q9a" align=center>\ <img src="sa1q16a" align=center>\ <center>= 1 250 cm/s2 = 12.5 m/s2.</center> [question17] type:2 caption:\ A boat decelerates in a straight line with a uniform acceleration of \ -0.5 m/s2. If its initial speed was 2.5 m/s, how many \ seconds is it until the boat comes to a standstill? correct:5.0 s wrong1:2.0 s wrong2:3.0 s wrong3:4.0 s feedback:\ speed change = final speed - initial speed\ <center>= 0.0 - 2.5 = -2.5 m/s</center>\ Because the boat is slowing down in a straight line, its velocity \ change is equal to its speed change.\ <img src="sa1q9a" align=center>\ so,\ <img src="sa1q17a" align=center>\ <center>= -2.5/-0.5 = 5.0 s.</center> [question18] type:1 image:1g16 caption:\ Water is dripping from a tank behind a tractor at the rate of one drip \ per second. The diagram shows the pattern of drips as the tractor \ drives along a paved road. What is the tractor's acceleration? correct:-0.1 m/s2 wrong1:0.0 m/s2 wrong2:0.1 m/s2 wrong3:-0.2 m/s2 feedback:\ The distance between drips decreases by 0.1 m every second. This means \ that the velocity changes by -0.1 ÷ 1.0 = -0.1 m/s every \ second.\ <img src="sa1q9a" align=center>\ <img src="sa1q18a" align=center>\ <center>= -0.1 m/s2.</center> [question19] type:2 caption:\ How long does it take a car to make a journey of 20 km if it is \ travelling at an average speed of 50 km/h? correct:24 minutes wrong1:20 minutes wrong2:30 minutes wrong3:50 minutes feedback:\ <img src="sa1q1a" align=center>\ so,\ <img src="sa1q1b" align=center>\ <img src="sa1q19a" align=center>\ <center>= 0.4 hour = 24 minutes.</center> [question20] type:2 caption:\ If a falling stone has an acceleration of 10 m/s2, what is \ its speed when it has been falling from rest in a straight line for \ 4.0 seconds? correct:40 m/s wrong1:20 m/s wrong2:4.0 m/s wrong3:2.5 m/s feedback:\ <img src="sa1q9a" align=center>\ so,\ velocity change = acceleration x time\ <center>= 10 x 4.0 = 40 m/s</center>\ Because the stone is falling in a straight line from rest, its speed \ change will equal its velocity change.