Please help me with the following questions.

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Activity 1: Free-Body Activity Given the following situations work with those around you to 1. Draw a picture and identify the forces. 2. Draw a complete free-body diagram for the object a. Use one color to represent the individual forces and another color to represent the net force. Situation 1: A heavy crate is being lowered straight down at a constant speed by a steel cable. Situation 2: A boy is pushing a box across the floor at a steadily increasing speed. Let the box be "the system" for analysis. Situation 3: A bicycle is speeding up down a hill. Friction is negligible, but air resistance is not. Situation 4: You've slammed on your car brakes while going down a hill. You're skidding to a halt. Activity 2: Problems With your group members solve the problems: 1. On a winter day a child of mass 20.0 kg slides on a horizontal sidewalk covered in ice. Initially she is moving at 3.00 m/s, but due to friction comes to a halt in 2.25 m. a. How much time is required for the girl to stop? b. What is the magnitude of the constant friction force that acts on her as she slides? 2. You make a conical pendulum using a string of length 0.800 m and a bob of mass 0.250 kg. When the bob is moving in a circle at a constant speed, the string is at an angle of 20.0' from the vertical. a. What is the radius of the circle around which the bob moves? b. How much time does it take the bob to complete one cycle? c. What is the tension in the string? Figure 1 L RWork and Kinetic Energy Activity 1: Determining Work and Change in Kinetic Energy With the people next to you, determine in each of the cases the different forces, sign (+ , -, or 0) of the work done by the forces, and the sign (+, - , or 0) in the change in kinetic energy. Example: An elevator moves up at a constant speed. Forces are gravity and tension. W = -, W =+, AK=0. 1. A descending elevator brakes to a halt. 2. A box slides up a frictionless slope. 3. A rope pulls a box to the left across a frictionless floor. 4. A car turns a corner at constant speed. Activity 2: Discussions With the people next to you, discuss the following questions and record your collective answers. 1. A nonzero net force acts on an object. Is it possible for any of the following quantities to be constant: (a) the object's speed, (b) the objects velocity, (c) the object's kinetic energy? 2. Why does going up the stairs quickly feel more difficult than going up the stairs at a steady pace, if the same amount of work is done? Activity 3: Problems With the people next to you, solve the following problems. A 0.100 kg box is attached to the end of a spring that is anchored to the wall on the left. The spring is initially unstretched. The box is given an initial velocity of 1.5 m/s to the right. How far along the horizontal surface will the box move if the spring constant of the spring is 20.0 N/m and the coefficient of kinetic friction is 0.47? Vo to O e