The Force Awakens
A 10kg object has two forces acting on it, Fₐ and Fb. If the object is decelerating, which of the following statements must be true?
a.) Fₐ + Fb ≤ 0
b.) Fₐ + Fb = 0
c.) Fₐ - Fb = 0
d.) Fₐ + Fb < 0
d.) Fₐ + Fb < 0
A 12kg block and 8kg block are connected by a frictionless pulley on a frictionless incline plane as shown:
What is the acceleration of the 12kg block?
a.) 1 m/s² up the incline
b.) 1.7 m/s² up the incline
c.) 3.3 m/s² down the incline
d.) 5 m/s² down the incline
a.) 1 m/s² up the incline
A block of mass m is sitting motionless on a plane with an incline of θ, a coefficient of static friction of μₛ, and a coefficient of kinetic friction μₖ. Which of the following will occur once the plane is elevated on one side, increasing θ?
a.)The maximum force caused by static friction will decrease.
b.) The maximum force caused by static friction will increase.
c.) The coefficient of kinetic friction
μₖ will decrease.
d.) The coefficient of static friction
μₛ will decrease.
a.)The maximum force caused by static friction will decrease.
A box of mass 10kg is sent to a planet with the same mass and three times the radius of Earth. What does the box weigh, in Newtons, on the surface of the new planet?
a.) 9 N
b.) 90 N
c.) 11 N
d.) 1N
c.) 11 N
Which of the following statements must additionally be true if it is determined that an object has zero acceleration?
A.) The object has zero velocity.
B.) There are no forces acting on the object.
C.) The object is not moving upwards or downwards.
D.) The object has no unbalanced forces acting on it.
D.) The object has no unbalanced forces acting on it.
A child pushes a 100 kg refrigerator with a force of 50 N, but the refrigerator does not move. Suppose the coefficient of static friction between the floor and the refrigerator is 0.4. What is the force due to friction in this scenario?
a.) 400 N
b.) 50 N
c.) 950 N
d.) 350 N
b.) 50 N
A stationary block has a normal force of 15N acting on it. The block is sitting on an inclined plane with an angle of 30ᵒ. What is the force of friction acting on it?
a.) 15 N
b.)11.4 N
c.) 6.3 N
d.) 8.7 N
d.) 8.7 N
An 8kg block is placed at the top of a plane inclined by
30ᵒ with a coefficient of kinetic friction of 0.1. What is the block’s acceleration down the ramp?
a.) 5 -√3/2 m/s²
b.) 5 - √5/2 m/s²
c.) 10 -√3/2 m/s²
d.) 10 - √5/2 m/s²
a.) 5 -√3/2 m/s²
On a different planet, a 50kg person weighs 400N. What is the acceleration due to gravity on this planet?
a.) 16 m/s²
b.) 0.13 m/s²
c.) 12 m/s²
d.) 8 m/s²
d.) 8 m/s²
Which of the following changes would increase the net acceleration of mass m down the frictionless inclined plane?
a.) Increasing the angle of θ
b.) Releasing the mass in the middle of the inclined plane
c.) Increasing the mass of m
d.) Increasing the length of the inclined plane
a.) Increasing the angle of θ
A 150 gram baseball is hit with enough force to give an acceleration of 60,000 m/s² by a 1.2 kg bat. What is the recoil acceleration of the baseball bat?
a.)60,000 m/s²
b.) 9000 m/s²
c.) 10,800 m/s²
d.) 7500 m/s²
d.) 7500 m/s²
An elevator is designed to carry a maximum weight of 9800 N (including its own weight), and to move upward at a speed of 5 m/s after an initial period of acceleration. What is the relationship between the maximum tension in the elevator cable and the maximum weight of the elevator while the elevator is accelerating upward?
a.) The tension is greater than 9800 N
b.) The tension is less than 9800 N
c.) The tension equals 9800 N
d.) It cannot be determined from the information given
a.) The tension is greater than 9800 N
A boy is pulling a 20kg sled attached to a 4m rope of negligible mass up a hill inclined at 30ᵒ above the horizontal. With what force should the boy pull on the rope in order to give the sled an acceleration of 2 m/s²? (The coefficient of kinetic friction between the sled and the incline is 0.2)
a.) 140 N
b.) 172 N
c.) 40 N
d.) 125 N
b.) 172 N
A 70kg man travels in a rocket up to an altitude equal to the Earth's radius. What is his weight, in Newtons, at this altitude?
a.) 172 N
b.) 343 N
c.) 686 N
d.) 858 N
a.) 172 N
A 1000 kg car is traveling south along a highway with a constant velocity of 26 m/s. What is the net force acting on the car?
0
A Ferrari with mass 1400 kg can accelerate from 0 to 60 mph in 3 seconds. What is the average force provided by the engine during this time? (1 mile = 1.6km)
a.) 4480N
b.) 28000N
c.) 12500N
d.)9800N
e.)1200N
c.) 12500N
Workers want to suspend a 40kg sign from a ceiling with cables, but the cables they have available are only able to support a maximum 10 N of force before snapping. If they are planning on suspending the cables at a 45° angle, what is the least number of cables that would be sufficient to support the sign without snapping the cables?
a.) 60 cables
b.) 80 cables
c.) 40 cables
d.) 20 cables
a.) 60 cables
A 50kg boat is floating at rest on the water when it is simultaneously hit by a southward current with force 100N and an eastward wind of force 75N. What is the magnitude of the velocity of the boat 3 seconds later?
a.) 20 m/s
b.) 12 m/s
c.) 6 m/s
d. 25 m/s
e.) 7.5 m/s
e.) 7.5 m/s