Force, Acceleration & Work PDF - Science 10

Force, Acceleration & Work ~ SCIENCE 10 ~  Force & Motion Objects at rest do not move because all forces acting on them are balanced. If forces become unbalanced (if one force is greater than another), then an object can gain motion....

Force, Acceleration & Work ~ SCIENCE 10 ~  Force & Motion Objects at rest do not move because all forces acting on them are balanced. If forces become unbalanced (if one force is greater than another), then an object can gain motion. The object on the table does not have motion because the force it exerts on the table is equal to the force the table exerts on it. What would have to happen to make the object move upwards? What would have to happen to make the object move downwards?  Net Force Force is defined as a push or a pull on an object. An object has many forces acting upon it; the sum of these forces is referred to as net force. When a vehicle is braking, for example, there are three different forces that act in the same direction, causing the vehicle to slow down (force of air resistance, force of friction, and the force applied by the brakes ). If these three forces overcome the force that is propelling the vehicle forward, then the vehicle’s net force will be negative, causing it to decelerate and eventually come to a stop.  The Effect of Mass Another factor that influences the rate of acceleration/deceleration of an object is the mass of that object. Objects with a greater mass have a more difficult time overcoming opposing forces. Heavier objects thus experience a decreased rate of acceleration/deceleration when a force is applied.  Newton’s Second Law of Motion This relationship between net force, mass, and acceleration is described by Newton’s second law of motion, which states that an object will accelerate in the direction of the net force acting upon it. * Note that force is measured in newtons (N). One newton is equivalent to one kg(m/s 2). PRACTICE 1. A child pulls on a 6.5 kg sled with a net force of 14.2 N. Determine the sled’s rate of acceleration. PRACTICE 1. A child pulls on a 6.5 kg sled with a net force of 14.2 N. Determine the sled’s rate of acceleration.  PRACTICE 2. A net force of 16.0 N is applied to a soccer ball with a mass of 0.25 kg. Calculate the ball’s rate of acceleration as it is kicked across a field.  PRACTICE 2. A net force of 16.0 N is applied to a soccer ball with a mass of 0.25 kg. Calculate the ball’s rate of acceleration as it is kicked across a field. PRACTICE 3. What net force would be required to cause a 0.040 kg object to accelerate at a rate of 100.0 m/s2 ?  PRACTICE 3. What net force would be required to cause a 0.040 kg object to accelerate at a rate of 100.0 m/s2 ?  PRACTICE 4. A net force of 5.00 N is applied to an object, causing it to accelerate at a rate of +2.50 m/s2. What must be the mass of the object?  PRACTICE 4. A net force of 5.00 N is applied to an object, causing it to accelerate at a rate of +2.50 m/s2. What must be the mass of the object? 5. A vehicle with a mass of 1250 kg travels at an average velocity of 45 km/h East when the driver engages the brakes to stop at an intersection. a) If the net force applied by the brakes is 7000.0 N West, determine the vehicle’s rate of deceleration. b) Determine the length of time that this net force must be applied in order for the vehicle to come to a complete stop. Complete the front side of Topic 5 Questions  Newton’s First Law of Motion In the absence of a net force, an object in motion will maintain its velocity, and an object at rest will remain at rest. This is referred to as Newton’s first law of motion. Newton’s first law explains why a space probe requires no engines to travel beyond the solar system. In deep space, there is no friction to slow things down, so the probe simply maintains its initial velocity.  Force & Work When a force is applied to an object, causing that object to move, then work is done on the object. ❖ Note that the force applied to the object must be greater than all other forces acting on the object in order to cause it to move, or perform work. ❖ Just because energy is exerted does not mean that work is occurring. Is any work being done on this wall?  Calculating Work The amount of work done on an object (in Joules) can be determined by multiplying the force applied to that object (in Newtons) by the distance that the object moves (in meters) Note that 1 Netwon-meter is equivalent to 1 Joule (the conventional unit of measurement for work) PRACTICE 1. You exerted a force of 25 N on your textbook while lifting it a height of 1.4 m to put it on a shelf. How much work did you do on your textbook? PRACTICE 1. You exert a force of 25 N on your textbook while lifting it a height of 1.4 m to put it on a shelf. How much work did you do on your textbook? PRACTICE 2. If the steam from an engine does 102.5 J of work, propelling an object a distance of 26 m, what force was exerted on that object by the steam?  PRACTICE 2. If the steam from an engine does 102.5 J of work, propelling an object a distance of 26 m, what force was exerted on that object by the steam? PRACTICE 3. How much force is required to perform 18.0 J of work on a cart over a distance of 3.0 m?  PRACTICE 3. How much force is required to perform 18.0 J of work on a cart over a distance of 3.0 m?  PRACTICE 4. Calculate the work done during a 7.5 s time interval to accelerate a 175 kg motorcycle from rest to a speed of 30.0 m/s over a distance of 108m.  PRACTICE 4. Calculate the work done during a 7.5 s time interval to accelerate a 175 kg motorcycle from rest to a speed of 30.0 m/s over a distance of 108m. Complete the back side of Topic 5 Questions