Learning Materials
Features
Discover
Chapter 4: Q25CQ (page 160)
Explain, in terms of the properties of the four basic forces, why people notice the gravitational force acting on their bodies if it is such a comparatively weak force.
The gravitational force being the weakest is still noticed because of its attractive nature.
Over 30 million students worldwide already upgrade their learning with 91影视!
All the tools & learning materials you need for study success - in one app.
Get started for free
Newton鈥檚 third law of motion tells us that forces always occur in pairs of equal and opposite magnitude. Explain how the choice of the 鈥渟ystem of interest鈥� affects whether one such pair of forces cancels.
An American football lineman reasons that it is senseless to try to out-push the opposing player, since no matter how hard he pushes he will experience an equal and opposite force from the other player. Use Newton鈥檚 laws and draw a free-body diagram of an appropriate system to explain how he can still out-push the opposition if he is strong enough.
Suppose your car was mired deeply in the mud, and you wanted to use the method illustrated in Figure 4.37 to pull it out.
(a) What force would you have to exert perpendicular to the center of the rope to produce a force of 12,000 N on the car if the angle is 2.00掳? In this part, explicitly show how you follow the steps in the Problem-Solving Strategy for Newton鈥檚 laws of motion.
(b) Real ropes stretch under such forces. What force would be exerted on the car if the angle increases to 7.00掳 and you still apply the force found in part (a) to its center?
A nurse pushes a cart by exerting a force on the handle at a downward angle 35.0潞 below the horizontal. The loaded cart has a mass of 28.0 kg, and the force of friction is 60.0 N.
(a) Draw a free-body diagram for the system of interest.
(b) What force must the nurse exert to move at a constant velocity?
A freight train consists of two 8.00脳104 -kg engines and 45 cars with average masses of 5.50脳104 kg.
(a) What force must each engine exert backward on the track to accelerate the train at a rate of 5.00脳10鈥�2 m/s2 if the force of friction is 7.50脳105 N, assuming the engines exert identical forces? This is not a large frictional force for such a massive system. Rolling friction for trains is small, and consequently trains are very energy-efficient transportation systems.
(b) What is the force in the coupling between the 37th and 38th cars (this is the force each exerts on the other), assuming all cars have the same mass and that friction is evenly distributed among all of the cars and engines?
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine