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TYPES OF FORCES AND NEWTON'S SECOND LAW When different types of forces act on an object and the net force is unbalanced, then it will cause a change in the velocity of the object. Newton's 2nd Law of Motion describes how unbalanced forces affects an object's motion, stating that the rate of acceleration depends on the amount of net force acting on an object's mass (F=ma). Formula Units Force= Mass (Acceleration) Newtons = kgm/s/s Acceleration = Force/Mass m/s/s or m/s2 Mass= Force/Acceleration kg 1. Two forces act on a skydiver with parachute open during a drop. The weight (W) of the person has a force of 500N down. The upward pull (P) of air resistance is 400 N. A. What are the two types of forces acting on the skydiver? ________________________________________________________ ________________________________________________________ B. What is the net force? C. If the skydiver has a mass of 50 kg, what is his acceleration? 2A. The boy is pulling the wagon to the left. What is his force called? _______________________________________________ 2B. What is the force acting in the opposite direction of the boy? __________________________________________________ 2C. Laura and her dog have a total mass of 40 kg. Her brother is pulling the wagon to the left. The acceleration rate of the wagon is 1 m/s2. What is the amount of force used by her brother to pull on the wagon? (Hint: Use force formula) 2D. If Laura gets out of the wagon, the mass of the wagon is now 15 kg. The acceleration rate of the wagon is still 1 m/s2. Will her brother need more force or less force to move the wagon with just the dog in it? Explain and prove it by showing your calculations. 3. The force of Miguel’s hand pushing the wooden block to the right is called the applied force. Miguel is pushing with a force of 39 N to the right. The force of friction is acting with a force of 13 N to the left. A. What are the two types of forces acting on the block? ______________________________________________ ______________________________________________ B. What is the magnitude and direction of the net force? C. Using the force that you just calculated, find the mass of the wooden block if its acceleration rate is 4 m/s/s. 4. Monica, a skydiver opens up her parachute during a drop. The force of gravity on the skydiver is 1,000N down. The force of air resistance on the skydiver is 800N up. A. What are the two types of forces acting on Monica? _____________________________________________ _____________________________________________ B. What is the magnitude and direction of the net force? C. If Monica has a mass of 40 kg, what is her rate of acceleration? 5. Picture A- Ball is at rest Picture B- Ball accelerates Picture C- Ball accelerates A. This scientist is holding a ball on Earth. In which Picture (A, B, C), is gravity acting on the ball? __________________________________________________________________________ B. In which Picture is the force of gravity equal to the applied force of the man’s hand holding the ball? ______________________________________________________________________________ 6. There is a spring scale on the right with a box attached to it. The box has a mass of 75 kg. A. What are the two forces acting on the box? ___________________________________________________________ ___________________________________________________________ B. When Timothy first added the box to the spring scale, the force of gravity on the object was 60 N and the spring force was 45 N. What is the magnitude and direction of the net force? C. What is the acceleration rate of the box? 7. A collision occurs when two or more objects hit each other. The first ball, a soccer ball, has a mass of 5 kg. The second ball, a basketball, has a mass of 10 kg. A. The soccer ball is moving and the basketball is not moving. If the soccer ball is moving to the right and hits the basketball, in which direction will the basketball move? B. The basketball has a mass of 10 kg. If it is accelerating at a rate of 3 m/s/s, what is the net force? C. Now, the soccer ball is not moving and the basketball is moving to the left. If the basketball hits the soccer ball, in which direction will the soccer ball move? D. If both the soccer ball and basketball move towards each other and collide with the same amount of force, which ball will accelerate at a greater rate and move a greater distance? Explain. *ANSWER KEY * ANSWER KEY * ANSWER KEY* TYPES OF FORCES AND NEWTON'S SECOND LAW When different types of forces act on an object and the net force is unbalanced, then it will cause a change in the velocity of the object. Newton's 2nd Law of Motion describes how unbalanced forces affects an object's motion, stating that the rate of acceleration depends on the amount of net force acting on an object's mass (F=ma). Formula Units Force= Mass (Acceleration) Newtons = kgm/s/s Acceleration = Force/Mass m/s/s or m/s2 Mass= Force/Acceleration kg 1. Two forces act on a skydiver with parachute open during a drop. The weight (W) of the person has a force of 500N down. The upward pull (P) of air resistance is 400 N. A. What are the two types of forces acting on the skydiver? The two types of forces are weight and air resistance. B. What is the net force? Net Force= 500 N down - 400 N up Net Force= 100 N down C. If the skydiver has a mass of 50 kg, what is his acceleration? A= F/M A= 100 N/50 kg A= 2 m/s/s 2A. The boy is pulling the wagon to the left. What is his force called? The force of the boy pulling on the wagon is called the applied force. 2B. What is the force acting in the opposite direction of the boy? The force acting in the opposite direction is friction. 2C. Laura and her dog have a total mass of 40 kg. Her brother is pulling the wagon to the left. The acceleration rate of the wagon is 1 m/s2. What is the amount of force used by her brother to pull on the wagon? (Hint: Use force formula) F= ma F= 40 kg ( 1 m/s/s) F= 40 N 2D. If Laura gets out of the wagon, the mass of the wagon is now 15 kg. The acceleration rate of the wagon is still 1 m/s2. Will her brother need more force or less force to move the wagon with just the dog in it? Explain and prove it by showing your calculations. F= ma F= 15 kg (1 m/s/s) F= 15 N Explanation: He uses less force (15 Newtons) to move the wagon with just the dog in it because there is less mass. When an object has less mass, less force is required to move the object. 3. The force of Miguel’s hand pushing the wooden block to the right is called the applied force. Miguel is pushing with a force of 39 N to the right. The force of friction is acting with a force of 13 N to the left. A. What are the two types of forces acting on the block? The two forces acting on the block is the applied force and the force of friction. B. What is the magnitude and direction of the net force? Net force= 39 N right - 13 N left Net force= 26 N right C. Using the force that you just calculated, find the mass of the wooden block if its acceleration rate is 4 m/s/s. M= F/A M= 26 N/ 4 m/s/s M= 6.5 kg 4. Monica, a skydiver opens up her parachute during a drop. The force of gravity on the skydiver is 1,000N down. The force of air resistance on the skydiver is 800N up. A. What are the two types of forces acting on Monica? The two types of forces acting on Monica is the force of gravity and air resistance. B. What is the magnitude and direction of the net force? Net Force= 1,000 N down- 800 N up Net Force= 200 N down C. If Monica has a mass of 40 kg, what is her rate of acceleration? A= F/M A= 200 N/ 40 kg A= 5 m/s/s 5. Picture A- Ball is at rest Picture B- Ball accelerates Picture C- Ball accelerates A. This scientist is holding a ball on Earth. In which Picture (A, B, C), is gravity acting on the ball? Since the scientist is on Earth, gravity is always acting on objects. Therefore, gravity is acting on the ball for all pictures A, B, and C. B. In which Picture is the force of gravity equal to the applied force of the man’s hand holding the ball? In Picture A, the force of gravity is equal to the applied force because the object is at rest. Forces are balanced and there is no change in the object's motion. 6. There is a spring scale on the right with a box attached to it. The box has a mass of 75 kg. A. What are the two forces acting on the box? The two forces acting on the box are the spring force and the force of gravity. B. When Timothy first added the box to the spring scale, the force of gravity on the object was 60 N and the spring force was 45 N. What is the magnitude and direction of the net force? Net Force= 60 N down - 45 N up Net Force= 15 N down C. What is the acceleration rate of the box? A= F/M A= 15 N/ 75 kg A= 0.2 m/s/s 7. A collision occurs when two or more objects hit each other. The first ball, a soccer ball, has a mass of 5 kg. The second ball, a basketball, has a mass of 10 kg. A. The soccer ball is moving and the basketball is not moving. If the soccer ball is moving to the right and hits the basketball, in which direction will the basketball move? The basketball will move to the right B. The basketball has a mass of 10 kg. If it is accelerating at a rate of 3 m/s/s, what is the net force? Net Force= MA= 10 kg (3 m/s/s) = 30 Newtons Right C. Now, the soccer ball is not moving and the basketball is moving to the left. If the basketball hits the soccer ball, in which direction will the soccer ball move? The soccer ball will move to the left D. If both the soccer ball and basketball move towards each other and collide with the same amount of force, which ball will accelerate at a greater rate and move a greater distance? Explain. The soccer ball will accelerate and move a greater distance because it has less mass compared to the basketball.
