Name ______Period ______

Warm-ups 4.1

1 Name, define, and write down the page numbers in the book where you would find Newton’s three laws of motion.

  1. What net force does a sliding crate experience when you exert a force of 110 N and friction between the crate and the floor is 110 N?
  2. Describe the motion of this crate.
  1. A book sitting on a shelf has a weight of 15 Newtons. The shelf would have to push upward with at least 15 Newtons to keep the book from falling. Which of Newton’s laws describes this idea?
  1. In a car you accelerate at a constant rate of 2m/s2. If you and the car have a total mass of 4100 kg, how much net force is the engine creating?
  1. Which law is used for question #2?
  1. Two people are riding in the same car. The driver steps on the gas and they change their speed. Is it possible for these two people to feel different forces when the driver increases the car’s speed? Explain your answer.
  1. You are standing on a skateboard (mass = 5 kg) and you want to jump off by pushing the skateboard one way so you will go the other way. If your mass is 65 kg and you push with a force of 50 N, what are the accelerations of you and the skateboard?

In a car, you are driving 60 m/s. A cat jumps out in front of you and so you slam on the brakes and come to a stop.

  1. What is the acceleration of the car if it takes 2.4 seconds to stop?
  1. What is the force the brakes apply to the car if the car’s total mass is 2605 kg?
  1. Would this force be greater, smaller or the same if you had more people in the car with you? Explain your answer.

A 78 kg person steps into an elevator

  1. How much force does the elevator have to support because of this person?
  1. If the elevator and the person have a combined mass of 1460 kg and the cables apply a total force of 14408 N, what is the net force?
  1. What is the acceleration?
  1. If the elevator accelerates for only 2 seconds, what is its final speed?
  1. After this acceleration, the elevator moves at a constant speed, what is the net force now?
  1. An airplane with a mass of 985 kg is trying to take off. At a given speed on the runway, the wings are creating a lift of 8000N. You will need to account for friction. The speed at this point is constant. Draw a free-body diagram with all forces that are involved.
  1. You are shoveling snow. One shovel-full you have 24 kg of snow and you accelerate the snow (throwing it) from rest to 3 m/s in one second. What is the force on the shovel?
  1. A jumbo jet cruises at a constant velocity of 1000 m/s when the thrusting force of its engines is a constant 100,000 N. What is the acceleration of the jet?
  1. What is the force of air resistance on the jet?
  1. If the net force acting on a sliding block is somehow tripled, by how much does the acceleration increase?
  2. If the mass of a sliding block is tripled while a constant net force is applied, by how much does the acceleration decrease?
  1. What is the net force that acts on a 10 N freely falling object?
  2. What is the net force that acts on a 10 N falling object when it encounters 4 N of air resistance?
  3. What is the net force that acts on a 10 N falling object when it encounters 10 N of air resistance?