Exam 2 Review

a rock is thrown vertically into the air. at the top of its path its acceleration is a. 10 m/s^2 b. zero c. between 0 and 10 m/s^2 d. greater than 10 m/s^2

a. 10 m/s^2 (hw: newton law)

a 160 lb person has a mass of 160/32 = 5 slugs. A 160 lb person steps into an elevator and stands on a bathroom scale. determine the scale reading for the given scenarios. The elevator accelerates upwards and is now moving at a constant speed. a. 160 lb b. 150 lb c. 170 lb

a. 160 lb (pop: Newton 2)

a brick is resting on a rough incline as shown in the figure. the friction force acting on the brick, along the incline, is a. less than the weight of the brick b. equal to the weight of the brick c. greater than the weight of the brick d. zero

a. less than the weight of the brick (hw: equi)

we discussed normal forces. normal a. meaning perpendicular to the surface b. meaning parallel to the surface c. meaning nothing is wrong with it d. meaning a regular contact force

a. meaning perpendicular to the surface (pop:equi)

when no forces act on objects their paths are normally a. straight lines b. all of the above c. circles d. ellipes

a. straight lines (pop:newton)

if more horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object a accelerates in the direction of the applied force b. none of the above c. experiences greater friction d. accelerates opposite the direction of the applied force

a accelerates in the direction of the applied force (hw: newton law)

if gravity between the sun and earth suddenly vanished, Earth would continue moving in a. straight-line path b. an outward spiral path c. a curved path d. an inward spiral path

a. straight-line path (Hw: newton law)

when a car goes around a circular curve a horizontal road at constant speed, what force causes it to follow the circular path? a. the friction force from the road b. gravity c. the normal force from the road d. no force causes the car to do this because the car is traveling at constant speed and therefore has no acceleration

a. the friction force from the road (hw: circular)

a karate expert executes a swift blow and breaks a cement block with her bare hand. the magnitude of the force on her hand is a. the same as the force applied to the block b. need more info c. more than the force applied to the block d. less than the force applied to the cement block e. zero

a. the same as the force applied to the block (hw: newton law)

for an object in uniform circular motion, its velocity and acceleration vectors are always perpendicular to each other at every point in the path a. true b. false

a. true (hw: circular)

a car is moving along a circle of radius R and its speed is V. If the car increases its speed by a factor of 3 (x3), the centripetal acceleration (or force) is (v= 1m/s, r=1m) a. x9 b. x1 c. x3 d. stays the same

a. x9

a push on a 1kg brick accelerates it. neglecting friction, equally accelerating a 10 kg brick requires a. 100 times as much force b. 10 times as much force c. one-tenth the amount of force d. just as much force e. none of the above

b. 10 times as much force (hw: newton law)

a 160 lb person has a mass of 160/32 = 5 slugs. A 160 lb person steps into an elevator and stands on a bathroom scale. determine the scale reading for the given scenarios. The elevator accelerates downwards at 2ft/s^2 a. 160 lb b. 150 lb c. 170 lb

b. 150 lb (pop: Newton 2)

dummy is pushing the crate with an applied force of 94N (@ right). the kinetic friction is 94N in magnitude. the crate has a. + acceleration b. acceleration = 0 c. a - acceleration

b. acceleration = 0 (pop:fric, equi)

the acceleration of a body is a. equal to the net force on the body b. always in the same direction as the net force on the body c. in the direction that the body is moving d. always in the same direction as its velocity

b. always in the same direction as the net force on the body (pop: Newton 2)

whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is a. greater with the brick wall b. both the same c. greater with the haystack

b. both the same (pop: impulse)

a karate chop is more effective if one's hand a. bounces upon impact b. follows through upon impact c. extends the time upon impact

b. follows through upon impact(hw: newton law)

when a boxer moves into an oncoming punch, the force experienced is a. no different, but the timing is different b. increased c. decreased d. all of the above

b. increased (pop: impulse)

You stand on a bathroom scale placed on an inclined plane (slope). The weight you are reading is called the apparent weight, that weight is a. more than your real weight b. less than your weight c. same as your real weight

b. less than your weight (pop:equi)

the impulse-momentum relastionship is direct result of a. newton's 3rd law b. newton's 2nd law c. newton's law of gravity d. newton's 1st law

b. newton's 2nd law (hw: newton law)

what is true about kinetic and static friction? a. it depend on the mass b. static > kinetic c. static < kinetic d. static =kinetic

b. static > kinetic (pop:fric, equi)

the net force on any object in equilibrium is a a. non-zero when motion is involved b. zero c. less than its weight d. equal to its weight

b. zero (hw: newton law)

the net force on any object in equilibrium is a. non-zero when motion is involved b. zero c. equal to its weight c. less than its weight

b. zero (pop:newton)

when a parachute reaches its terminal speed, the net force is a. @ down b. @ up c. 0

c. 0 (pop:fric, equi)

a 160 lb person has a mass of 160/32 = 5 slugs. A 160 lb person steps into an elevator and stands on a bathroom scale. determine the scale reading for the given scenarios. The elevator is accelerating upwards at 2 ft/s^2 a. 160 lb b. 150 lb c. 170 lb

c. 170 lb (pop: Newton 2)

Arnold Strongman and Suzie Small each pull very hard on opposite ends of a massless rope in a tug-of-war. The greater force on the rope is exerted by a. suzie b. arnold c. both the same

c. both the same (pop:newton)

the force that accelerates a rocket in outer space is exerted on the rocket by the a. atmospheric pressure b. rocket's wings c. exhaust gases d. rocket's nose cone e. none of the above

c. exhaust gases (pop: newtons)

dummy pushes a 50 kg crate and it is moving. there is kinetic friction opposing the push. If the push increases then a. kinetic friction increases as well b. kinetic friction decreases c. kinetic friction stays the same (constant)

c. kinetic friction stays the same (constant) (pop:fric, equi)

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it a. moves along a straight-line path away from the center of the circle b. moves along a straight-line path toward the center of the circle c. moves along a straight-line path in its original direction d. moves along a path that is neither straight nor circular e. continues to follow a circular path, but with a radius larger than the original radius.

c. moves along a straight-line path in its original direction (hw: circular)

when a rocket ship gaining speed in outer space runs out of fuel, it a. gains speed for a short time, slows down and eventually stops b. gains speed for a short time, then slows down to a constant velocity c. no longer gains speed

c. no longer gains speed (hw: newton law)

compared with falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the a. stopping time is shorter on the carpet b. carpet provides a smaller impulse and longer time c. stopping time is longer on the carpet d. carpeted floor provide a smaller impulse

c. stopping time is longer on the carpet (hw: newton law)

when a boxer is moving away from a punch, the force experienced is reduced because a. the force is less effective b. momentum transfer is reduced c. the time of contact is increased d. all of the above

c. the time of contact is increased (pop:impulse)

A Mack truck and a Volkswagen traveling at the same speed collide head-on. The impact force is greatest on the a. mack truck b. same for both c. volkswagen

c. volkswagen (hw: newton law)

the greater efficiency achieved with the curved blades of a Pelton wheel is due to a. rotational momentum b. greater time of water impact c. divided impulse d. bouncing

d. bouncing (pop: newton)

a cannon recoils while firing a cannonball. the speed of the cannon's recoil is relatively small because a. momentum of the cannon is smaller b. momentum is mainly concentrated in the cannonball c. force against the cannon is smaller than against the ball d. cannon has much more mass than the cannonball

d. cannon has much more mass than the cannonball (pop: impulse)

it is correct to say that impulse is equal to a. momentum b. velocity multiplied by time c. forced multiplied by the distance it acts d. corresponding change in momentum

d. corresponding change in momentum (hw: newton law)

a car is moving along a circle of radius R and its speed is V. If the car decreases its speed by a factor of 2 (divided by 2), the centripetal acceleration (or force) is (v = 4m/s, r= 1m) a. divided by 2 b. stays the same c. divided by 6 d. divided by 4

d. divided by 4 (hw: circular)

a car is moving along a circle of R and its speed is V. If for the same speed, the radius is divided by 3 then the acceleration (v= 1m/s, R= 6) a. divided by 6 b. divided by 3 c. is multiplied by 9 d. is multiplied by 3

d. is multiplied by 3 (hw: circular)

when a boxer is moving away from a punch, the force experienced is reduced because a. force is less effective b. momentum transfer is reduced c. all of the above d. the time of contact is increased

d. the time of contact is increased (hw: newton law)

to catch a fast-moving ball, you extend you hand forward before contact with the ball and let it ride backward in the direction of the ball's motion. doing this reduced the force of contact on your hand principally because the a. time of contact is decreased b. force of contact is reduced c. relative velocity is less d. time of contact is increased e. none of the above

d. time of contact is increased (hw: newton law)

when an object moves in uniform circular motion, the direction of its acceleration is a. is directed away from the center of its circular path b. in the same direction as its velocity vector c. depends on the speed of the object d. in the opposite direction of its velocity vector e. is directed toward the center of its circular path

e. is directed toward the center of its circular path (hw: circular)

if an object travels at a constant speed in a circular path, the acceleration of the object is a. zero b. in the opposite direction of the velocity of the object c. smaller in magnitude the smaller the radius of the circl e d. in the same direction as the velocity of the object e. larger in magnitude the smaller the radius of the circle

e. larger in magnitude the smaller the radius of the circle (hw:circular)