Physics 1-5 Questions & Answers

Physics 1-5 Questions & Answers A 400kg bear grasping a vertical tree slides down at constant velocity. What is the friction force that acts on the bear? - ANSWER: The bear is sliding down the tree at a constant speed (dynamic equilibrium) so the acceleration of the bear (and net force on the bear) is zero. This means that the force on the bear due to friction balances the force on the bear due to gravity. Ffriction = Fgravity = ma = (400 kg)*(10 m/s2) = 4000 N. acceleration: - ANSWER: the rate at which velocity changes with time; the change in velocity may be in magnitude, or direction, or both (acceleration= change of velocity/time interval) acceleration= - ANSWER: fnet/m As speed increases for an object in free fall, does acceleration increase also? - ANSWER: : No, the acceleration due to gravity (the only acceleration a body in free fall experiences) is the same. The increased speed comes from the constant acceleration As you leap upward in a standing jump, how does the force that you exert on the ground compare with your weight? - ANSWER: The force exerted on the ground as you jump is greater than your weight, which is why you are able to move upward. If the jump wasn't greater than your weight there would be no net upward force and you wouldn't leave the ground. ( Asteroids have been moving through space for billions of years. What keeps them moving? - ANSWER: Nothing keeps asteroids moving. They are "happily" moving through space in a state of dynamic equilibrium. Objects like the Sun and Earth can change their motion but after this brief interaction they again move off at some constant speed average speed: - ANSWER: the total distance traveled divided by the time of travel (av speed=total distance/time interval) Can a car with a velocity toward the north simultaneously have an acceleration toward the south? - ANSWER: If your car is travelling North and you apply the brakes to slow it down it will have an acceleration in a direction to the South - so yes you can have a car travelling North and accelerating to the South. Can you say that no force acts on a body at rest? Or is it correct to say that no net force acts on it? - ANSWER: We know that if a body is at rest the sum of forces (net force) acting on the body is zero. This is