Motion/Projectiles
A woman drives 10 kilometers to work and returns home for lunch, what is her total displacement?
0
Impulse = (Force)(time)
J = Ft
What is mass measured in?
kilograms
What is the equation for centripetal force?
Fc = mv2/r
What is the formula for Work?
Work = (Force)(Distance)
W = Fd
What is the slope of a Velocity v. Time graph?
Acceleration
What are the two ways to find momentum?
mΔv and FΔt
(Mass)(Change in Velocity) and (Force)(Change in Time)
What is the mass of a child who weighs 500 Newtons?
fw = mg
m = fw/g
m = 500/9.8
51.02 kg
What is the difference between centripetal and centrifugal force?
Centripetal force refers to the inward seeking force that causes circular motion. Centrifugal force refers to the sensation of a force in the outward direction that is caused by the inertia of an object. It is not a real force.
How is one way you can change the amount of potential energy in an object? Explain.
Because potential energy is (mass)(acceleration due to gravity)(height), you can either increase the mass of the object OR put the block at a greater height.
Does mass affect the rate (acceleration) at which an object falls? EXPLAIN
No, all objects fall with the same acceleration when in free fall (9.8 m/s2)
What is the relationship between the total momentum of 2 objects before and after a collision?
The total momentum before collision is equal to the total momentum after collision. This is the law of conservation of momentum.
What does intertia do?
Resists change in motion
What is the difference between G and g?
‘G’ is the universal gravitational constant shared by all bodies affected by gravity; ‘g’ is the acceleration of gravity ON EARTH
Two boys, Mark and Carl, are pushing a box of 50 kg along a level frictionless road. They each exert the same force, 100 newtons, on the same block for 20 meters. How much work did they exert on the block?
W = Fd
W = (100)(20)
W = 2000 J
Find the final velocity of a car moving from rest while accelerating at 49m/s2, over a distance of 9m.
Vf2 = V02 + 2ad
Vf2 = 0 + 2(49)(9)
√Vf2 = √882
Vf2 = 29.7 m/s
A hockey player takes a shot and strikes a 0.25 kg puck traveling at 1.5 m/s with his hockey stick and increases its velocity to 2.5 m/s. What is the change in momentum?
ΔP = m Δv
ΔP = .25(2.5 - 1.5)
ΔP = .25 kg m/s
If the forces exerted on an object are 10N to the east and 40N to the west, what is the net force exerted on the object?
30N west
A ball is traveling in a circle on a string. The radius is .35 m and the period is .38 seconds, what is the balls velocity?
V = 2πr/T
V = (2π)(.35)/(.38)
V = 5.79 m/s
What is the Work-Energy Theorem?
The work done by all forces acting on a particle equals the change in the particle's kinetic energy.
What is Vy at the peak of a projectile?
0
Robert, who has a mass of 70.0 kg, is riding at 43.0 m/s in her red sports car when she must suddenly slam on the brakes to avoid hitting a deer crossing the road. She strikes the air bag, that brings her body to a stop in 0.8 s. What average force does the seat belt exert on her?
Ft = mΔv
F = (mΔv)/t
F = (70)(0 - 43)/(.8)
F = -3,762.5 N
A 8 kg block has a sliding coefficient of friction of 0.53. If the brick is sliding to the right with a constant velocity, what is the magnitude of the force of friction?
Ff = μFn
Ff = (.53)(9.8)(8)
Ff = 41.55N
Indicate if the gravitational force would increase or decrease and by what numerical factor. (Inverse square law – “rule of ones”): If the distance between the 2 masses is doubled and BOTH mass amounts are also doubled.
Hint: g = GM1M2/r2
g = GM1M2/r2
g = (1)(2)(2)/(22)
g = 1 (would stay the same)
Drew lifts a 76-kg crate onto a truck bed 5 meters high in 2.7 seconds. Connor lifts sixty 7-kg boxes on to the same truck in a time of 120 seconds. Who produced more power?
P = W/t
PDrew = (76)(5) / (2.7) PConnor = (60)(7)(5) / (120)
PDrew = 140.7 Watts PConnor = 17.5 Watts
Drew produced the greater power