Physics 201L

Four students use different instruments to measure the length of the same pen. Which measurement implies the greatest precision? (a) 160.0 mm. (b) 16.0 cm. (e) Need more information. (c) 0.160 m. (d) 0.00016 km.

(a) 160.0 mm

The number 0.0078 has how many significant figures? (a) 1. (b) 2. (c) 3. (d) 4.

(b) 2.

How many significant figures does 1.362 + 25.2 have? (a) 2. (b) 3. (c) 4. (d) 5.

(b) 3.

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 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 10m/s east. Another car travels 10m/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.

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

(b) 120°.

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.

A hunter is aiming horizontally at 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 the bullet are falling downward 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.

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.

Accuracy represents (a) repeatability of a measurement, using a given instrument. (b) how close a measurement is to the true value. (c) an ideal number of measurements to make. (d) how poorly an instrument is operating.

(b) how close a measurement is to the true value.

A ball is thrown downward at a speed of 20 ms. 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 ms2 downward. (a) v = (20 m/s) - gt. (b)y = y0 + (-20m/s)t - (1/2)gt2. (c)v2 =(20m/s)2 -2g(y-y0). (d) (20 m/s) = (v + v0)/2. (e) All of the above.

(b)y = y0 + (-20m/s)t - (1/2)gt2. (c)v2 =(20m/s)2 -2g(y-y0).

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.

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 of 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 baseball is hit high and far. Which of the following statements is true? At the highest point, (a)the magnitude 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.

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/s2 up. (c) v =0, a = 9.8 m/s2 down (d) v =9.8 m/s up, a = 0. (e) v =9.8 m/s down, a = 0.

(c) v =0, a = 9.8 m/s2 down

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.

[L2] represents the dimensions for which of the following? (a) cm2. (b) square feet. (c) m2. (d) All of the above.

(d) All of the above.

At time t = 0 an object is traveling to the right along the ±x axis at a speed of 10.0 ms with acceleration -2.0 m/s2. 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.

Which of the three kicks in Fig. 3-32 is in the air for the longest time? They all reach the same maximum height h. Ignore air resistance. (a), (b), (c), or (d) all the same time.

(d) all the same time.

To convert from ft2 to yd2, you should (a) multiply by 3. (b) multiply by 1/3. (c) multiply by 9. (d) multiply by 1/9. (e) multiply by 6. (f) multiply by 1/6.

(d) multiply by 1/9.

A student's weight displayed on a digital scale is 117.2 lb. This would suggest her weight is (a) within 1% of 117.2 lb. (b) exactly 117.2 lb. (c) somewhere between 117.18 and 117.22 lb. (d) somewhere between 117.0 and 117.4 lb.

(d) somewhere between 117.0 and 117.4 lb.

Which is not true about an order-of-magnitude estimation? (a) It gives you a rough idea of the answer. (b) It can be done by keeping only one significant figure. (c) It can be used to check if an exact calculation is reasonable. (d) It may require making some reasonable assumptions in order to calculate the answer. (e) It will always be accurate to at least two significant figures.

(e) It will always be accurate to at least two significant figures.

Which of the following should be part of solving any problem in physics? Select all that apply: (a) Read the problem carefully. (b) Draw a picture of the situation. (c) Write down the variables that are given. (d) Think about which physics principles to apply. (e) Determine which equations can be used to apply the correct physics principles. (f) Check the units when you have completed your calculation. (g) Consider whether your answer is reasonable.

All

A car travels along the x axis with increasing speed. We don't know if to the left or the right. Which of the graphs in Fig. 2-34 most closely represents the motion of the car?

concave down

A baseball player hits a ball that soars high into the air. After the ball has left the bat, and while it is traveling upward (at point P in Fig. 3-31), what is the direction of acceleration? Ignore air resistance.

downward direction