Two identical wooden blocks sit on a table. One block is balanced on top of the other. If the bottom block is removed, will the total potential energy of the blocks increase, decrease or stay the same?
A. Increase
B. Decrease
C. Stay the same
D. It is not possible to tell
The correct answer is: B. Decrease
Rationale: The total potential energy of the blocks is due to their height above the table. When the bottom block is removed, the height of the top block is halved, so its potential energy is halved. The bottom block now has zero potential energy as it is at the same height as the table.
Every day, a scientist places 50 bacteria into a petri dish. The bacteria population doubles every hour. How long, to the nearest hour, will it take for the bacteria population in the petri dish to exceed 1,000,000?
A. 14
B. 7
C. 13
D. 15
The correct answer is: A. 14
Rationale: After 7 hours, the bacteria population will be 50 * 2^7 = 6400. After 14 hours, the population will be 6400 * 2^7 = 1,024,000.
A train departs from London and travels 50 miles north. It then turns and travels 50 miles west. It then turns again and travels 50 miles south. It then turns a final time and travels 50 miles east. At the end of its journey, how far is the train from its starting point?
A. 50 miles
B. 200 miles
C. 0 miles
D. 100 miles
The correct answer is: C. 0 miles
Rationale: After traveling 50 miles north and then 50 miles south, the train is back to its original latitude. After then travelling 50 miles west and 50 miles east, the train is back to its original longitude.
John and Mary both tell lies on Mondays, Tuesdays and Wednesdays, but tell the truth on all other days of the week. John says, "Yesterday I told a lie." Mary says, "So did I." What day of the week is it?
A. Thursday
B. Friday
C. Wednesday
D. Tuesday
The correct answer is: A. Thursday
Rationale: If it were Monday, Tuesday or Wednesday, they would have both told the truth when they said they lied yesterday. This is a contradiction. If it were Friday, Saturday or Sunday, they would both have lied when they said they lied yesterday. This is also a contradiction. So it must be Thursday.
If all bloops are zerts and all zerts are quirps, then which of the following statements must be true?
A. All bloops are quirps.
B. Some zerts are bloops.
C. All quirps are zerts.
D. Some quirps are not bloops.
The correct answer is: A. All bloops are quirps.
Rationale: If all bloops are zerts, and all zerts are quirps, then all bloops must also be quirps.
A farmer has 10 trees in a row. He wants to plant a new tree between each existing pair of trees, and also at each end of the row. How many trees will he have when he is finished planting?
A. 21
B. 19
C. 20
D. 18
The correct answer is: A. 21
Rationale: The farmer starts with 10 trees. He plants 9 trees between the existing trees, and 2 trees at the ends of the row. This gives a total of 10 + 9 + 2 = 21 trees.
If a ball bounces half as high on each bounce as it did on the previous bounce, how many bounces will it take before the height of the bounce is less than 10% of the original height?
A. 4
B. 5
C. 3
D. It is not possible to tell.
The correct answer is: A. 4
Rationale: After one bounce, the ball will be at 50% of its original height. After two bounces, it will be at 25%, after 3 bounces it will be at 12.5%, and after 4 bounces it will be at 6.25% of its original height.
There are 5 red socks and 3 blue socks in a drawer. If you close your eyes and take out socks at random, how many socks must you take out to be certain that you have at least one pair of socks of the same colour?
A. 3
B. 5
C. 2
D. 4
The correct answer is: D. 4
Rationale: In the worst case, you could pick 1 red sock, then 1 blue sock, then 1 red sock. The next sock you pick, whether it is red or blue, will guarantee you have a pair.
A man is looking at a portrait. He says, "Brothers and sisters I have none, but that man's father is my father's son." Who is in the portrait?
A. It is not possible to tell
B. The man's son
C. Himself
D. The man's father
The correct answer is: B. The man's son
Rationale: "My father's son" is the man himself. Therefore, the man in the portrait is the son of the man looking at the portrait.
A racecar driver is driving around a circular track. If he is halfway around the track and has travelled one mile, what is the total length of the track?
A. 1 mile
B. 2 miles
C. 4 miles
D. It is not possible to tell
The correct answer is: B. 2 miles
Rationale: If the driver has travelled one mile when he is halfway around the track, then the full track is twice this distance, which is 2 miles.