Chapter 5 Review
1)
A 50 N force acts on an object at an angle of 40 degrees above the positive x axis. What is the horizontal
component of this force?
What is the vertical component of this force?
2)
A crate getting dragged along the horizontal ground is being pulled by a 20 N force at an angle of 30 degrees
above the horizontal. If the crate has a mass of 5 kg and there is no friction, what is its acceleration?
3)
Which of Newton’s Laws (1, 2, or 3) explains each of the following phenomena?
a. _____ A satellite can stay in orbit for many years at the same speed without any fuel being used.
b. _____ When swimming you push backwards on the water so that you may go forward
c. _____ It takes a semi-truck much longer to accelerate to top speed than it does a sports car
d. _____ The Moon’s gravity pulls just as hard on the Earth, as the Earth’s gravity pulls on the Moon
e. _____ If a driver is not wearing his seatbelt during a car accident he will be thrown forward through
the windshield.
f.
_____ A spaceship can only accelerate in space by ejecting something (typically gas) into space
g. _____ When the opening to an inflated balloon is released it will accelerate forward
h. _____ When a car crashes, it undergoes an extremely fast acceleration…. the quicker the
acceleration the more force the car, and the driver will encounter.
i.
_____ If each are being pulled by a 2 N force, a 5 kg cart will accelerate 5 times slower than will a 1
kg cart
j.
_____ It takes a train a lot longer time to slow down than it does a car
k. _____ A car filled with cinder blocks is harder to slow down than the car without the cinder blocks
l.
_____ When punching a brick wall it is likely that you can break your hand.
m. _____ In the 1970’s NASA launched a probe into space, even though its fuel ran out shortly after
launch this probe is still travelling further and further away, just recently reaching regions outside of
our solar system.
4) A car is stuck because its wheels are stuck spinning in the mud, could several individuals sitting on the trunk
of the car be an effective way to get the car unstuck?
5)
What two things affect how much friction exists between two surfaces?
6) A 70 kg man stands on a bathroom scale in an elevator. If while in the elevator the bathroom scale reads 715
N, what is the magnitude and direction of the elevator’s acceleration?
7) Which is larger for a given object, the force of static friction or the force of kinetic friction?
8) It takes 100 N of force to start a 1000 kg crate into motion.
a. What is the force of static friction between the crate and ground?
b. What is the coefficient of static friction between the crate and ground?
9)
A 30 kg mass is suspended from a spring and it is stretched a distance of 20 cm. What is the spring constant
of the spring?
10) A 40 kg cart is getting pulled by a 140 N Force, if there exists a coefficient of kinetic friction between the cart
and road of .10 what will be the acceleration of the cart?
11) If we consider the ‘action’ force to be the Earth’s gravity pulling an object downward, what would be the
‘reaction’ force?
12) Does gravity pull harder on a more massive object?
13) Does gravity make more massive objects accelerate faster?
14) Aristotle determined that a constant force produces a constant velocity? Explain why or why not
15) On a boat a 100 N force acts due east, and a 120 N force acts at 65° N of E.
a. What is the net force on the object?
b. If the boat has a mass of 20 kg, what is the boat’s acceleration?
16) What is the net force on a 350 kg crate if a truck is pulling it with a force of 2500 N and the coefficient of
kinetic friction between the crate and ground is .45.
b) Is the crate accelerating? If so how fast?
17) What net force is needed to accelerate a .02 kg bullet from rest to a speed of 300 m/s over the length of the
barrel of the gun of 0.60 m?
18) How do you know if an object is in equilibrium?
19) Find the Tension in each wire
40°
10 kg
20)
A
There is a coefficient of kinetic friction of .28 between block
A and the table. And Block
B has a mass of 4.7 kg.
If block
A has a mass of 3.4 kg what will be the acceleration of the
system?
B
21) An object connected to a string is being swung around in a circle… if the string breaks what type of path does
it follow?
22) A 70 kg skydiver is falling toward Earth at a constant velocity, what is the magnitude of the force of air
resistance acting on him?
23) A horizontal 52-N force is needed to slide a box across a flat surface at a constant velocity of 3.5 m/s. What is
the coefficient of kinetic friction between the box and the floor?