Momentum, Impulse, Work, Power Harmandip Singh, Nasif Mahmud, Mohammed Yeashin, and Ajla Dupljak

Momentum Momentum – a measurement of the tendency of an object to stay in motion. SI Unit: [kg-m/s] Formula: momentum = (mass)(velocity) or p = mv - The momentum of a body is proportional to both its mass and velocity. If wither one increases the momentum will also increase. - Momentum is a vector quantity whose direction is the same as the object's velocity.

Impulse Impulse- the product of the net force acting on an object and the time during which the force acts. The symbol for impulse is J. SI Unit: [kg-m/s] or [Ns] (Equivalent to momentum)The unit for impulse and the unit for momentum are equivalent. The Impulse is also the change in momentum for an object in motion.

Calculating Impulse J= F net(T) = ΔP (Force)(Time) = Impulse [kg * m/s 2 ] Δp= mΔv – Δp= m(v’-v) – Δp= mv’-mv – Δp= p’-p

Practicing with Momentum and Impulse 1. If the mass of an object is 5kg, and the velocity is 7m/s, what is the momentum? 2. What is the value of the momentum of a 10 kg ball running down a bowling alley at a speed of 5 m/s? 3. A gust of wind exerts a 300. N net force on a kg sailboat for 15 s. What is the change in the momentum and velocity of the boat?

Solutions 1. Formula first : p = mv p = (5kg)(7 m/s) 35 kg-m/s 2. Formula first: p = mv p = (10 kg)(5 m/s) 50 kg-m/s 3. Formula first : J =Ft, p=mv J= (300.N)(15 s)= 4500 Ns J= Δp= 4500kg-m/s p=mv v=p/m= (4500kg-m/s)/(1000.kg)= 4.5m/s HW: AMSCO pg #153, 162, 170

Work Work: In physics, work is done whenever a force acts on an object in the direction of the objects motion. If an object is not in motion no work is being done. Si Unit: J (Joule) 1J = 1newton · meter = 1N · m - Work is the product of the magnitude of the applied force F and the objects displacement d in the direction of the force. -When calculating force only the force parallel to the objects motion can be used. -Work is a scalar quantity

Power Power is the amount of work done per unit time. Like work, it is a scalar quantity. The symbol for power is P. Power = (work/time) o P=W/t o Since W=Fd, we can write: P= (Fd/t). o Since v= d/t we can write: P= (Fd/t)=Fv. Thus, power can also be expressed as the product of the applied force and the velocity of the object SI Unit = Watts --> J/Sec

Practicing with Work and Power 1. How much work is done on a downhill skier by an average braking force of 9.8 × 10 2 Newtons to stop her in a distance of 10. meters? 2. What is the work required to raise a kilogram box from the surface of the earth to a height of 5.0 meters? 3. If energy is supplied at the rate of 10 watts, how much work is done during 2 seconds?

Solutions 1. Formula first: W=Fd W= 9.8 × 10 2 N ·10.m W= 9.8 ×10 3 J 2. Formulas first: w=mg, W=Fd w= 10.kg × 9.8 m/s 2 w= 98. N W=Fd W= 98.N ×5.0m W= 490J 3. Formula first: P=W/t Pt=W 10watts × 2s= W 20J=W

Work and Power Demonstration HW: AMSCO pg #1, 9, 17

PEACE