Physics and Math Chapter 1
What is the most common system of measurement?
The metric system (Composed of SI units)
A 1000 kg rocket ship, travelling at 1000m/s is acted upon by an average force of 20kN applied in the direction of its motion for 8 s. What is the change in velocity of the rocket? a. 160 m/s b.260 m/s c. 160,000 m/s d. 260,000 m/s
160 m/s
Which of the following statements is true of movement on a plane with friction? 1. Acceleration is a function of applied force only 2. more force is needed to accelerate a stationary object than an identical moving object 3. the force of friction is independent of the mass of objects.
2
A man walks 30 m east and then 40 m north. What is the difference between his traveled distance and his displacement? a. 0m b. 20m c. 50m d. 70m
20m
A car is traveling at 40 km/hr and the driver puts on the brakes, bringing the car to rest in a time of 6s. What is the magnitude of the average acceleration of the car? a.240 km/hr2 b. 12,000 km/hr2 c. 24,000 km/hr2 d. 30,000 km/hr2
24,000 km/hr2
A 10 kg wagon rests on an inclined plane. The plane makes an angle of 30 degrees with the horizontal. Approximately how large is the force required to keep the wagon from sliding down the plane (Note: sin 30 = 0.5, cos30=0.866)? a. 10 N b. 49 N C. 85 N d. 98 N
49 N
A BASE jumper runs off a cliff with a speed of 3 m/s. Which of the following is closest to his speed after 0.5 seconds? a. 3m/s b. 6 m/s c. 8 m/s d. 10 m/s
6 m/s
A 30kg girl sits on a seesaw at a distance of 2m from the fulcrum. Where must her father sit to balance the seesaw if he has a mass of 90 kg? a. 67 cm from the girl b. 67 cm from the fulcrum c. 133 cm from the girl d. 267 cm from the fulcrum
67 cm from the fulcrum
Can a moving object be in equilibrium? Why or why not?
A moving object can be in either translational or rotational equilibrium (or both). Translational equilibrium only requires the net force on an object be zero - its velocity is constant. The corresponding condition in rotational equilibrium is that net torque equals zero -- its angular velocity is constant.
How is a scalar calculated from the product of two vectors? How is a vector calculated?
A scalar is calculated from two vectors using the dot product: A · B = lAl lBl cos Ꝋ. A vector is calculated by using the cross product: Ax B = lAl lBl sin Ꝋ.
When no force is being applied, the velocity must be:
Constant. if there is no net force acting on an object, then that object is not experiencing an acceleration and it has a constant velocity.
True or False: The Earth creates a larger force on you than you create on the Earth
False. Forces are always reciprocal in nature. When the Earth exerts a force of the same magnitude on the Earth (in the opposite direction). The difference in masses gives the Earth an apparent acceleration of zero.
True or False: If C = A x B, where A is directed toward the right side of the page and B is directed to the top of the page, then C is directed midway between A and B at 45 degree angle.
False. The would be true of an addition problem in which both vectors have equal magnitude, but it is never true for vector multiplication. To find the direction of C, we must use the right-hand rule. If the thumb points in the direction of A, and the fingers point in the direction of B, then our palm, C, points of of the page.
What is newtons third law?
For any two interacting objects, all forces acting on one object have an equal and opposing force acting on the other object.
Name two forces in addition to mechanical manipulation (pushing or pulling forces created by contact with an object):
Gravity and frictional forces were discussed in this chapter. Electrostatic, magnetic, elastic, weak nuclear, and strong nuclear forces are other examples of forces.
What is the equation for centripetal acceleration?
If the equation for centripetal force is Fc=mv2/r and force is simply mass times acceleration per Newton's second law, the ac=v2/r
What is the relationship between instantaneous velocity and instantaneous speed? Between average velocity and average speed?
Instantaneous speed is the magnitude of the instantaneous velocity vector. Average speed and average velocity may be unrelated because speed does not depend on displacement, but is rather the total distance traveled divided by time.
If you have an object three times as heavy as you can lift, how could a lever be used to life the object? Where would the fulcrum need to be placed?
One could place the fulcrum one quarter of the way across the lever, closer to the object. The ratio of the lever arms would then be 3:!, which means that only one third of the original force is necessary. (Alternatively, the fulcrum could be palced at the end with the object one-third of the way across the lever., This would again result in a 3:1 ratio of lever arms, meaning that only one-third of the original force is necessary.
During a test crash, a 500 kg car is driven at a constant velocity of 50 mph until it hits a wall without braking. Apply Newton's first law to this situation.
Prior to the collision the vehicle is travelling at constant velocity, which (according to Newton's first law) indicates that there is no acceleration and no net force.
During a test crash, a 500 kg car is driven at a constant velocity of 50 mph until it hits a wall without braking. Apply Newton's second law to this situation.
The collision with the wall creates a sudden deceleration. Because there is acceleration, there must be a net force. The value of the net force can be calculated by multiplying the mass of the car times the acceleration.
When calculating frictional forces, how is directionality assigned?
The direction of the frictional force always opposes movement. Once the instantaneous velocity vector is known (or net force, in the case of static friction), the frictional force must be in the opposite direction.
Describe the characteristics of displacement.
The displacement vector connect the object's initial position and its final position. Only accounts for the net change in position from initial to final. vector
When will the displacement be equal to 0?
The final position is the same as the starting position.
At a place where g=9.8 m/s2, an object is thrown vertically downward with a speed of 5 m/s while a different object is thrown vertically upward with a speed of 10 m/s. Which object undergoes a greater change in speed in a time of 2 s? a. the first object has a greater change in speed b. the second object has a greater change in speed c. both objects undergo the same change in speed d. it cannot be determined from the information given
The first object has a greater change in speed
A firefighter jumps horizontally from a burning building with an initial speed of 1.5 m/s. At what time is the angle between his velocity and acceleration vectors the greatest? A. The instant he jumps B. When he reaches terminal velocity C. Halfway through his fall D. Right before he lands on the ground
The instant he jumps
How do the forces acting in free fall and projectile motion differ?
The only force acting in both free fall and projectile motion is gravity
At what angle of launch is a projectile going to have the greatest horizontal displacement? What angle will result in the greatest vertical displacement assuming a level surface?
The produce of sine and cosine is maximized when the angle is 45 degrees. Because horizontal displacement relies on both measurements, the maximum horizontal displacement will also be achieved at this angle. Vertical displacement will always be zero as the object returns to the starting point. Objects launched vertically will experience the greatest vertical distance.
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
The tension is greater than 9800 N.
What methods are generally used when determining the resultant of the vectors?
The tip-to-tail method Breaking each vectors into perpendicular component such as x and y.
True or False: total distance traveled can never be less than the total displacement.
True. Displacement considers the most direct route between two points. distance will always be equal or larger in magnitude than displacement.
During a test crash, a 500 kg car is driven at a constant velocity of 50 mph until it hits a wall without braking. Apply Newton's third law to this situation.
When the car collides with the wall, the car exerts a force on the wall. Simultaneously, the wall exerts a force of equal magnitude in the opposite direction on the car.
What is newtons first law?
a body either at rest or in motion with constant velocity will remain that way unless a net force acts upon it . known as the law of inertia in the absence of any forces -- or when the net force is zero -- there will be no change in velocity
What is newtons second law?
an object of mass m will accelerate when the vector sum of the forces results in some nonzero resultant force vector. Acceleration results from the sum of the force vectors
Order the following from smallest to largest? centimeter, angstrom, inch,mile, foot
angstrom<centimeter<inch<foot<mile
which of the following expressions correctly illustrates the SI base unites for each of the variables in the formula below? m(delta v) = F (delta t) a. lb x mph = ft x lb x s b. kg x m/s = N x s c. kg x m/s = (kgxm)/s2 x s d. g x m/s = (gxm)/s2 x s
c. kg x m/s = (kgxm)/s2 x s
centrifugal force is an apparent outward force during circular motion. It has been described as a reaction force according to Newton's third law. Which of the following statements is most likely to be correct regarding centrifugal force? a. centrifugal force exists only for uniform circular motion, not nonuniform circular motion. b. centrifugal force exists only when tension or a normal force provides centripetal acceleration. c. centrifugal force always acts anti parallel to the centripetal force vector. d. centrifugal force is result of repulsive electrostatic interactions.,
centrifugal force always acts anti parallel to the centripetal force vector.
What are the basic quantities that relate to kinematics?
displacement, velocity and acceleration
Which of the following quantities is NOT a vector? a. velocity b. force c. displacement d. distance
distance
What are vectors?
numbers that have a magnitude and direction
What are scalars?
numbers that have magnitude only and no direction
A rock (m=2 kg) is shot up vertically at the same time that a ball (m = 0.5 kg ) is projected horizontally. If both start from the same height: a. the rock and ball will reach the ground at the same time b. the rock will reach the ground first c. the ball will reach the ground first d. the rock and ball will collide in the air before reaching the ground
the ball will reach the ground first
A 20 kg wagon is released from rest from the top of a 15 m long lane, which is angled at 30 degrees with the horizontal. Assuming that there is friction between the ramp and the wagon, how is this frictional force affected if the angel of the incline is increased? a.the frictional force increase b. the frictional force decreases c. the frictional force remains the same d. it cannot be determined from the information given
the frictional force decreases
What is a resultant?
the sum or difference of two or more vectors
Describe the characteristics of velocity?
vector magnitude = rate of change of displacement in a given amount of time SI units = m/s
When calculating the sum of vectors A and B (A+B) we put the tail of B at the tip of A. What would be the effect of reversing this order (B+A)?
vector addition unlike vector multiplication is a commutative function. The resultant of A+B is the same as B+A, so there would be no difference between the two resultants.
When calculating the difference of vectors A and B (A-B) we invert B and put the tail of this new vector at the top of A. What would be the effect of reversing this order (B-A)?
vector subtraction unlike vector multiplication is a commutative function. The resultant of A-B has the same magnitude as B-A, but is oriented in the opposite direction.
Provide a definition for displacement or velocity in terms of the other variable.
velocity is a rate of change of the displacement of an object. Displacement is a function of velocity acting over a period of time.
