Homework 3 1. When you push horizontally on a crate on a level floor that doesn't slide, how great is the force of friction on the crate? 2. As you increase your push, will friction on the crate increase also? 3. Once the crate is sliding, how hard do you push to keep it moving at constant velocity? 4. If the mass of a sliding block is somehow tripled at the same time the net force on it is tripled, how does the resulting acceleration compare with the original acceleration? 5. Calculate the weight in newtons of a person who has a mass of 50 kg. 6. Consider a 40-kg block of cement that is pulled sideways with a net force of 200 N. Show that its acceleration is 5 m/s2 . 7. Boxes of various masses are on a friction-free, level table. Rank each of the following based on acceleration from greatest to least: A B 5 N 10 10 N 15 N 5 kg 10 ko 15 N 5 N 15 N 5 kg -20 kg 8. Which contains more apples: a 1-pound bag of apples on Earth or a 1-pound bag of apples on the Moon? Which contains more apples: a 1-kilogram bag of apples on Earth or a 1-kilogram bag of apples on the Moon? 9. A race car travels along a raceway at a constant velocity of 200 km/h. What horizontal net force acts on the car? 10. Free fall is motion in which gravity is the only force acting. (a) Is a skydiver who has reached terminal speed in free fall? (b) Is a satellite above the atmosphere that circles Earth in free fall? 11. Why does a cat that accidentally falls from the top of a 50-story building hit a safety net below no faster than if it fell from the 20th story? 12. When you whirl a can at the end of a string in a circular path, what is the direction of the force you exert on the can