1. How much work does a person do in pushing a box with a force of 10 N over a distance of 4.0 m in the direction of the force? (A) 0.4 J (B) 4.0 J (C) 40 J (D) 400 J (E) 4000 J 2. A person pushes a 10 kg box at a constant velocity over a distance of 4 m. The coefficient of kinetic friction between the box and the floor is 0.3. How much work does the person do in pushing the box? (A) 12 J (B) 40 J (C) 75 J (D) 120 J (E) 400 J 3. How much work does the force of gravity do in pulling a 10 kg box down a 30Âº inclined plane of length 8.0 m? Note that sin 30 = cos 60 = 0.500 and cos 30 = sin 60 = 0.866. (A) 40 J (B) 69 J (C) 400 J (D) 690 J (E) 800 J 4. How much work does a person do in pushing a box with a fo rce of 20 N over a distance of 8.0 m in the direction of the force? (A) 1.6 J (B) 16 J (C) 160 J (D) 1600 J (E) 16000 J 5. The figure below is a force vs. displacement graph, showing the amount of force applied to an object by three different people. Al applies force to the object for the first 4 m of its displacement, Betty applies force from the 4 m point to the 6 m point, and Chuck applies force from the 6 m point to the 8 m point. Which of the three does the most work on the object?
(B) (C) (D) (E)
Betty Chuck Al and Chuck do the same amount of work Betty and Chuck do the same amount of work a car’s speed doubles, what happens to its kinetic energy? is quartered is halved is unchanged is doubled is quadrupled
6. When (A) It (B) It (C) It (D) It (E) It
7. A worker does 500 J of work on a 10 kg box. If the box transfers 375 J of heat to the floor through the friction between the box and the floor, what is the velocity of the box after the work has been done on it? (A) 5 m/s (B) 10 m/s (C) 12.5 m/s (D) 50 m/s (E) 100 m/s 8. A person on the street wants to throw an 8 kg book up to a person leaning out of a window 5 m above street level. With what velocity must the person throw the b ook so that it reaches the person in the window? (A) 5 m/s (B) 8 m/s (C) 10 m/s (D) 40 m/s (E) 50 m/s Questions 9 and 10 refer to a forklift lifting a crate of mass 100 kg at a constant velocity to a height of 8 m over a time of 4 s. The forklift then holds the crate in place for 20 s. 9. How much power does the forklift exert in lifting the crate? (A) 0 W (B) 2.0 10 3 W (C) 3.2 10 3 W (D) 2.0 (E) 3.2 10 4 W 10 4 W
10. How much power does the forklift exert in holding the crate in place? (A) 0 W (B) 400 W (C) 1.6 10 3 W (D) 4.0 10 3 W (E) 1.6 10 4 W
Acceleration Practice Problems
1. A car starts off stopped at the ramp light onto I5. When the light turns green it increases its speed to 30 m/s in 8s. a) What is the car's acceleration during those 8s?
b) Fill in the table below for the instantaneous speed of the car for ever second between 0s to 8s. Time 0s Elapsed Instantaneous Speed 1s 2s 3s 4s 5s 6s 7s 8s
2. A skateboarder starts off going up a ramp at 10m/s. When she reaches the top of the ramp, 1.5s later, she comes to a complete stop. What was her acceleration on the ramp? (Hint remember the sign of your answer will tell you if the acceleration represents speeding up or slowing down.)
3. A powder blue mini-van is tearing along a straight road when it’s driver sees a black cat in the road. It slows from 90miles/hour to 20 miles/hour in 10 seconds. What is the car’s acceleration? (Hint your answer should be in miles/hour/s.)
4. Mrs Mihata’s Mazda can accelerate at 5miles/hr/s. If she is already going 20miles/hr and then accelerates for 6 seconds how fast is she going when she is finished accelerating?
b. Fill in the table below to find her instantaneous speed at each second as she accelerates. Time 0s Elapsed Instantaneous Speed 1s 2s 3s 4s 5s 6s
5. A jet airplane accelerates from rest at 5 m/s/s for 16.4 s before taking off. How fast is it going when it leaves the ground?
b. Convert the speed you just found is #5 from m/s to miles/hr?
6. A fast car accelerates at 10 mi/hr/s from a...
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