Forces & Motion

Inertia Inertia- The amount of force needed to move an object.

How Can Unbalanced Forces Affect Objects? Acceleration is caused by unbalanced forces: slow down speed up stop start change direction change shape In your notes, describe an example of an unbalanced force affecting an object.

Mass and Weight Mass is the amount of stuff (matter) in an object. The mass of an object will remain the same anywhere in the universe. Mass is measured in grams or kilograms. Weight is the mass (kg) of an object multiplied by the acceleration of gravity (9.8 m/s2). The weight of an object depends on the gravitational pull of the location in the universe. The gravitational pull on the Moon is only 1/6 of Earth’s gravitational pull. Weight is measured in newtons (N).

Mass and Weight Example: F=ma A person with a mass of 25 kg x 9.8 m/s2 gravitational acceleration is equal to 245 N of weight force. F= 25 kg x 9.8 m/s2 F = 245 N The person exerts 245 N of force on the ground. If the person went to the Moon, they would only weigh 1/6 of 245 N.

Force Force (N) = mass (kg) x acceleration (m/s2) F ÷ m x a

Force Acceleration (m/s2) = force (N) ÷ mass (kg) F ÷ m x a

Force Mass (kg) = force (N) ÷ acceleration (m/s2) F ÷ m x a

Practice The acceleration of a sprinter is 10 m/s2. The force exerted on the starting blocks is 650 N. What is the mass of the sprinter? Force = Mass = Acceleration =

Check Your Answer The acceleration of a sprinter is 10 m/s2. The force exerted on the starting blocks is 650 N. What is the mass of the sprinter? Force = 650 N Mass = 65 kg Acceleration = 10 m/s2 Mass = force ÷ acceleration Mass = 650 ÷ 10 Mass = 65

Practice A 50 kg cart is accelerating at 15 m/s2. Calculate the force exerted on the cart? Force = Mass = Acceleration =

Check Your Answer A 50 kg cart is accelerating at 15 m/s2. Calculate the force exerted on the cart? Force = 750 N Mass = 50 kg Acceleration = 15 m/s2 Force (N) = mass (kg) x acceleration (m/s2) Force = 50 x 15 Force = 750

Practice A boat is pulling a 54 kg wake boarder. She accelerates at 2 m/s2. Calculate the force that is causing the acceleration. Force = Mass = Acceleration =

Check Your Answer A boat is pulling a 54 kg wake boarder. The force the boat is exerting on her is 108 N. Calculate her acceleration. Force = 108 N Mass = 54 kg Acceleration = 2 m/s2 Acceleration = force ÷ mass Acceleration = 108 ÷ 54 Acceleration = 2