Problem: Rough surfaces create more friction than smooth surfaces. Thats why cars have tires. Its also why we use rubber mats in areas that might get wet. In your bathtub, you may even use No-Slip tape. No-slip is another way of saying the items has a lot of friction. In Figure 1.9, the blades of the skates are very smooth. Thats why you cant slide across ice with shoes. The soles of your shoes are much rougher than skates. The rougher surface of shoes causes more friction and slows you down. Heavier objects also have more friction. A heavy object presses down with more force. The surfaces are held together more tightly. This makes the surfaces harder to slide past each other. Did you ever try to push something heavy across the floor? Heavy objects are much harder to push than light objects.

Question: "Why do heavier objects create more friction?"

Answer: "Press down with more force"

OPTIONS:
- no
- yes
Answer: yes

Problem: (CNN) -- Argentina's star-studded line-up began their World Cup campaign with a 1-0 victory over Nigeria in their Group B opener in Johannesburg on Saturday. A goal from defender Gabriel Heinze after six minutes was all that separated the two teams after an inspired display from Nigeria goalkeeper Vincent Enyeama. But South Korea ended the day on top of the group following a 2-0 victory over Greece in Port Elizabeth earlier on Saturday. Goals from Lee Jung-Soo and Park Ji-Sung gave the 2002 semifinalists a comfortable win over the 2008 European cvhampions. Argentina 1-0 Nigeria Enyeama could do little to stop Heinze's powerful early header from a Juan Sebastian Veron corner, but he kept his team alive with a string of acrobatic saves to deny World Player of the Year Lionel Messi. Diego Maradona was delighted to secure his first victory as a World Cup coach, but critical of his strikers for failing to make the game safe. "When you don't kill things off in front of goal you can pay a heavy price. They almost got a draw -- we missed loads of chances," Maradona told AFP. "Players such as Leo Messi and Higuain knocked in around 60 goals last season between them, yet today it was almost as if they couldn't set their sights on goal. "But the win means we can be calm -- we are in the right track."

Question: "Who did Argentina play on the opening game?"

Answer: "Portugal"

OPTIONS:
- no
- yes
Answer: no

Problem: Rolfe put down the little dog he had been holding, and went out into the hall. The dog accompanied him, frisking about him in friendly fashion. Rolfe first examined the bedroom that he had seen Inspector Chippenfield enter. It was a small room, containing a double bed. It was prettily furnished in white, with white curtains, and toilet-table articles in ivory to match. A glance round the room convinced Rolfe that it was impossible for a man to secrete himself in it. The door of the wardrobe had been flung open by the inspector, and the dresses and other articles of feminine apparel it contained flung out on the floor. There was no other hiding-place possible, except beneath the bed, and the ruthless hand of the inspector had torn off the white muslin bed hangings, revealing emptiness underneath. Rolfe went out into the hall again, and entered the room next the bedroom. This apartment was apparently used as a dining-room, for it contained a large table, a few chairs, a small sideboard, a spirit-stand, a case of books and ornaments, and two small oak presses. Plainly, there was no place in it where a man could hide himself. The next room was the bathroom, which was also empty. Opposite the bathroom was a small bedroom, very barely furnished, offering no possibility of concealment. Then the passage opened into a large roomy kitchen, the full width of the rooms on both sides of the hall, and the kitchen completed the flat.

Question: "In what room did Rolfe find a double bed?"

Answer: "The bedroom"

OPTIONS:
- no
- yes
Answer:
yes