Honors Physics

Chapter 5 Practice Problems1) A force of 3.0 N acts through a distance of 12 m in the direction of the

force. Find the work done.

2) How large a force is required to accelerate a 1300 kg car from rest to a speed of 20.0 m/s in a horizontal distance of 80.0 m?

3) Given the diagram, assume that the object is being pulled along the ground by a 75 N force directed 28° above the horizontal. How much work does the force do in pulling the object a displacement s = 8.0 m? Oh, and don’t freak out…”s” is sometimes used to represent displacement.

4) A block moves up a 30.0° incline under the action of certain forces, three of which are shown in the diagram below. F1 is horizontal and of magnitude 40. N. F2 is normal to the inclined plane and has a magnitude of 20. N. F3 is parallel to the plane and of magnitude 30. N. Determine the work done by each force as the block moves 80.0 cm up the incline.

5) A 300.0 g object slides 80.0 cm along a horizontal tabletop. How much work is done in overcoming friction between the object and the table if the coefficient of kinetic friction is 0.20?

6) How much work is done against gravity in lifting a 3.0 kg object through a vertical distance of 40. cm?

7) Compute the work done against gravity by a pump that discharges 600.0 L of oil into a tank 20. m above the pump’s intake. One cubic centimeter of fuel oil has a mass of 0.82 g. Also note that 1 L = 1000cm3.

8) A 2.0 kg mass falls 400.0 cm.a. How much work was done by the gravitational force?b. How much gravitational PE did the mass lose?

9) A force of 1.50 N acts on a 0.20kg cart so as to accelerate it along an air track. The track and force are horizontal and in line. How fast is the cart going after acceleration from rest through 30.0 cm? Ignore friction.

10) A 0.50 kg block slides across a tabletop with an initial velocity of 20.0 cm/s and comes to rest in a distance of 70.0 cm. Find the average friction force that impeded the object’s motion.

11) A car going 15 m/s is brought to rest in a distance of 2.0 m as it strikes a big pile of dirt. What is the average force exerted by seatbelts on a 90.kg passenger as the car is stopped?

12) A projectile is shot upward from Earth with a speed of 20.0 m/s. Using energy considerations, how high is the projectile when its speed is 8.0 m/s. Ignore air friction, and also ignore your desire to use the kinematics equations to solve this problem…could you go that route? YES. But I want you to see that considerations to energy can produce the exact same answer. If anything, use both methods and verify that you have the right answer by getting the same answer in both cases!!

13) Maybe I was the only child that had toys like these growing up, but we’ll try the problem anyway!! The diagram below shows a bead sliding on a curved metal wire. If frictional forces are negligible, and the bead has a speed of 200. cm/s at point A, what will be its speed:

a. At point Bb. At point C

Give your answers with two significant figures in both cases.

14) Use the same diagram as shown in problem 13. Suppose the bead has a mass of 15 g and a speed of 2.0 m/s at A, and it stops as it reaches point C. The length of wire from A to C is 2.5 meters. How large of an average frictional force opposed the motion of the bead?

15) The figure below shows a bead sliding on a wire. How large must height h1 be if the bead, starting at rest at A, is to have a speed of 200.0 cm/s at point B? Ignore friction.

16) Consider the diagram from #15 for this problem. Let h1 = 200. cm and h2

= 150 cm. At A, the 3.00 kg bead has a downward speed along the wire of 800 cm/s.

a. How fast is the bead moving as it passes point B if friction is negligible?

b. How much energy did it lose to friction work if it rises to a height of 20.0 cm above C after it leaves the wire?

17) A 1200.0 kg car is coasting down a 30.0° hill as shown in the diagram below. At a time when the car’s speed is 12 m/s, the driver applies the brakes. What constant force F (parallel to the road) must result if the car is to stop after traveling 100.0 m?

18) A ball at the end of a 180. cm long string swings as a pendulum as shown in the diagram below. The ball’s speed is 400.0 cm/s as it passes through its lowest position.

a. To what height h above this position will it rise before stopping?b. What angle does the pendulum then make with the vertical?

19) A 500.0 g block is shot up an incline with an initial speed of 200.0 cm/s. How far up the incline will the block go if the coefficient of friction between it and the incline is 0.150?

20) A 60,000. Kg train is being pulled up a 1.0% grade (meaning it rises 1.0 meters for every 100. horizontal meters) by a drawbar pull of 3.0 kN. The friction force opposing the motion of the train is 4.0 kN. The train’s initial speed is 12 m/s. Through what horizontal distance s will the train move before its speed is reduced to 9.0 m/s?

21) Mr. Wilson claims that his 1200kg car can accelerate from rest to a speed of 25 m/s in a time of 8.0 seconds. What average power must the motor produce to cause this acceleration? Give your answer in both watts and horsepower (conversions are available in the front of your textbook, FYI).

22) A 0.25 hp motor is used to lift a load at the rate of 5.0 cm/s. How great a load can it raise at this constant speed?

23) Repeat problem 21 (Wilson’s car) if the data apply to Wilson’s car going up a 20.° incline.