Physics Multiple Choice (Ch. 2 - 4)

A 50-N crate sits on a horizontal floor where the coefficient of static friction between the crate sand the floor is 0.50. A 20-N force is applied to the crate acting to the right. What is the resulting static friction force acting on the crate? a. 20 N to the right. b. 20 N to the left. c. 25 N to the right. d. 25 N to the left. e. None of the above; the crate starts to move.

b. 20 N to the left.

You drop a rock off a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their velocities? a. Both increase at the same rate. b. The velocity of the first rock increases faster than the velocity of the second. c. The velocity of the second rock increases faster than the velocity of the first. d. Both velocities stay constant.

a. Both increase at the same rate

A truck is traveling horizontally to the right. When the truck starts to slow down, the crate on the (frictionless) truck bed starts to slide. In what direction could the net force be on the crate? a. No direction. The net force is zero. b. Straight down (because of gravity). c. Straight up (the normal force). d. Horizontal and to the right. e. Horizontal and to the left.

a. No direction. The net force is zero.

A bullet fired from a rifle begins to fall... a. as soon as it leaves the barrel. b. after air friction reduces its speed. c. not at all if air resistance is ignored.

a. as soon as it leaves the barrel.

A car travels 10 m/s east. Another car travels 10 m/s north. The relative speed of the first car with respect to the second is a. less than 20 m/s b. exactly 20 m/s c. more than 20 m/s

a. less than 20 m/s

To pull an old stump out of the ground, you and a friend tie two ropes to the stump. You pull on it with a force of 500 N to the north while your friend pulls with a force of 450 N to the northwest. The total force from the two ropes is: a. less than 950 N b. exactly 950 N c. more than 950 N

a. less than 950 N

Which statements are NOT valid for a projectile? Take up as positive. a. The projectile has the same x velocity at any point on its path. b. The acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends. c. The acceleration of the projectile is a constant negative value. d. The y component of the velocity of the projectile is zero at the highest point of the projectile's path. e. The velocity at the highest point is zero.

b. The acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends. e. The velocity at the highest point is zero.

You are adding vectors of length 20 and 40 units. Which of the following choices is a possible resultant magnitude? a. 0 b. 18 c. 37 d. 64 e. 100

c. 37

You are riding in an enclosed train car moving at 90 km/h. If you throw a baseball straight up, where will the baseball land? a. In front of you. b. Behind you. c. In your hand. d. Can't decide from the given information.

c. In your hand.

Suppose an object is accelerated by a force of 100 N. Suddenly a second force of 100 N in the opposite direction is exerted on the object, so that the forces cancel. The object... a. is brought to rest rapidly. b. decelerates gradually to rest. c. continues at the velocity it had before the second force was applied. d. is brought to rest and then accelerates in the direction of the second force.

c. continues at the velocity it had before the second force was applied.

A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path? a. v = 0, a = 0. b. v = 0, a = 9.8 m/s^2 up. c. v = 0, a = 9.8 m/s^2 down. d. v = 9.8 m/s up, a = 0.

c. v = 0, a = 9.8 m/s^2 down.

You are trying to push your stalled car. Although you apply a horizontal force of 400 N to the car, it doesn't budge, and neither do you. Which force(s) must also have a magnitude of 400 N? a. The force exerted by the car on you. b. The friction force exerted by the car on the road. c. The normal force exerted by the road on you. d. The friction force exerted on the road on you.

a. The force exerted by the car on you. b. The friction force exerted by the car on the road. d. The friction force exerted on the road on you.

The magnitude of a component of a vector must be: a. less than or equal to the magnitude of the vector b. equal to the magnitude of the vector c. greater than or equal to the magnitude of the vector. d. less than, equal to, or greater than the magnitude of the vector

a. less than or equal to the magnitude of the vector

You are in the middle of a large field. You walk in a straight line for 100 m, then turn left and walk 100 m more in a straight line before stopping. When you stop, you are 100 m from your starting point. By how many degrees did you turn? a. 90 b. 120 c. 30 d. 180 e. This is impossible. You cannot walk 200 m and be only 100 m away from where you started.

b. 120

A hunter is aiming horizontally at a a monkey who is sitting in a tree. The monkey is so terrified when it sees the gun that it falls off the tree. At that very instant, the hunter pulls the trigger. What will happen? a. The bullet will miss the monkey because the monkey falls down while the bullet speeds straight forward. b. The bullet will hit the monkey because both the monkey and the bullet are falling downward at the same rate due to gravity. c. The bullet will miss the monkey because although both the monkey and bullet are falling downwards due to gravity, the monkey is falling faster. d. It depends on how far the hunter is from the monkey.

b. The bullet will hit the monkey because both the monkey and the bullet are falling downward at the same rate due to gravity.

A golf ball is hit with a golf club. While the ball flies through the air, which forces act on the ball? Neglect air resistance. a. The force of the golf club acting on the ball. b. The force of gravity acting on the ball. c. The force of the ball moving forward through the air. d. All of the above. e. Both (a) and (c).

b. The force of gravity acting on the ball.

One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level? a. The dropped ball. b. The thrown ball. c. Neither - they both have the same speed on impact. d. It depends on how hard the ball was thrown.

b. The thrown ball.

A ball is thrown downward at a speed of 20 m/s. Choosing the +y axis pointing up and neglecting air resistance, which equation(s) could be used to solve for other variables? The acceleration due to gravity is g = 9.8 m/s^2 downward. a. v = (20 m/s) - gt b. y = y_0 + (-20 m/s)t - (1/2)gt^2 c. v^2 = (20 m/s^2) - 2g(y - y_0) d. (20 m/s) = (v + v_0)/2 e. all of the above

b. y = y_0 + (-20 m/s)t - (1/2)gt^2 c. v^2 = (20 m/s^2) - 2g(y - y_0)

You drive 4 km at 30 km/h and then another 4 km at 50 km/h. What is your average speed for the whole 8-km trip? a. More than 40 km/h. b. Equal to 40 km/h. c. Less than 40 km/h. d. Not enough information.

c. Less than 40 km/h

A ball is dropped from the top of a tall building. At the same instant, a second ball is thrown upward from the ground level. When the two balls pass one another, one on the way up, the other on the way down, compare the magnitudes of their acceleration: a. The acceleration of the dropped ball is greater. b. The acceleration for the ball thrown upward is greater. c. The acceleration of both balls is the same. d. The acceleration changes during the motion, so you cannot predict the exact value when the two balls pass each other. e. The accelerations are in opposite directions.

c. The acceleration of both balls is the same

A person stands on a scale in an elevator. His apparent weight will be the greatest when the elevator... a. standing still. b. is moving upward at a constant velocity. c. is accelerating upward. d. is moving downward at constant velocity. e. is accelerating downward.

c. is accelerating upward.

When a skier skis down a hill, the normal force exerted on the skier by the hill is... a. equal to the weight of the skier. b. greater than the weight of the skier. c. less than the weight of the skier.

c. less than the weight of the skier.

A baseball is hit high and far. Which of the following statements is true? At the highest point... a. the magnitude of the acceleration of the acceleration is zero. b. the magnitude of the velocity is zero. c. the magnitude of the velocity is the slowest. d. more than one of the above is true. e. none of the above are true.

c. the magnitude of the velocity is the slowest.

In which of the following cases does a car have a negative velocity and a positive acceleration? A car that is traveling in the... a. -x direction at a constant 20 m/s b. -x direction increasing in speed c. +x direction increasing in speed d. -x direction decreasing in speed e. +x direction decreasing in speed

d. -x direction decreasing in speed

At time t = 0 an object is traveling to the right along the +x axis at a speed of 10.0 m/s with acceleration -2.0 m/s^2. Which statement is true? a. The object will slow down, eventually coming to a complete stop. b. The object cannot have a negative acceleration and be moving to the right. c. The object will continue to move to the right, slowing down but never coming to a complete stop. d. The object will slow down, momentarily stopping, then pick up speed moving to the left.

d. The object will slow down, momentarily stopping, then pick up speed moving to the left.

A bear sling is used in some national parks for placing backpackers' food out of the reach of bears. As the backpacker raises the pack by pulling down on the rope, the force (F) needed: a. decreases as the pack rises until the rope is straight across. b. doesn't change. c. increases until the rope is straight. d. increases but the rope always sages where the pack hangs.

d. increases but the rope always sages where the pack hangs.

You are pushing a heavy box across a rough floor. When you are initially pushing the box and it is accelerating... a. you exert a force on the box, but the box does no exert a force on you. b. the box is so heavy it exerts a force on you, but you do not exert a force on the box. c. the force you exert on the box is greater than the forces of the box pushing back on you. d. the force you exert on the box is equal to the force of the box pushing back on you. e. the force that the box exerts on you is greater than the force you exert on the box.

d. the force you exert on the box is equal to the force of the box pushing back on you.

Matt is able to pull a large truck because... a. he is stronger than the truck. b. he is heavier in some respects than the truck. c. he exerts a greater force on the truck than the truck exerts back on him. d. the ground exerts a greater friction force on Matt than it does on the truck. e. the truck offers no resistance because its brakes are off.

d. the ground exerts a greater friction force on Matt than it does on the truck.

The normal force on an extreme skier descending a very steep slope can be zero if... a. his speed is not great enough. b. he leaves the slope (no longer touches the snow). c. the slope is greater than 75 degrees. d. the slope is vertical (90 degrees).

d. the slope is vertical (90 degrees).