Physics Review Question Unit: Mass Year: 1992 Question#: 15 Question: Two rocks weighing 5 newtons and 10 newtons, respectively, fall freely from rest near the Earth's surface. After 3 seconds of free-fall, compared to the 5 newton rock, the 10-newton rock has greater: (1 ) acceleration (2 ) height (3 ) momentum (4 ) speed What is this question really asking? Explanation by: Joe W. [ Return to question menu ] Answer 1 acceleration INCORRECT- because of the neglection of air friction the two rocks would be accelerating at a same rate. return to top Answer 2 height INCORRECT- because they are falling at the same rate, their height's will be the same. return to top Answer 3 momentum CORRECT - even their velocity's are the same, the masses are different. Momentum is mass times velocity. p=mv so the momentum of the 10 newton rock will be greater than the momentum of the 5 newton rock. return to top Answer 4 speed Incorrect Because they are falling at the same rate, their speed's wil be the same. return to top What's this question really asking? As the 10N rock and the 5 Newton rock fall , what thing will be different after 3 seconds? return to top |
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