MULTIPLE CHOICE: Choose the best that completes the statement or answers the que

Question

MULTIPLE CHOICE: Choose the best that completes the statement or answers the question.

MULTIPLE CHOICE: Choose the one alternative that best completes the statement or answers the question 1.) A reasonable estimate for the duration of a typical physics lecture is A) 1000 s B) 10,000 s C) 600 s D) 3,500 s 2.) You drive 6.0 km at 50km/h and then another 6.0 km at 90 km/h. Your average speed over the 12 km drive will be A) less than 70 km/h B) greater than 70 km/h C) equal to 70 km/h D) exactly 38 km/h F) It cannot be determined from the information given because we must also know directions traveled 3.) Suppose that a car traveling to the west begins to slow down as it approaches a traffic light. Which of the following statements about its acceleration is correct? A) The acceleration is zero B) Since the car is slowing down, its acceleration must be negative C) The acceleration is toward the east D) The acceleration is toward the west 4.) When a ball is thrown straight up with no air resistance, the acceleration at its highest point A) is upward B) is downward C) reverses from downward to upward D) reverses from upward to downward E) is zero 5.) For general projectile motion with no air resistance, the horizontal component of a projectile's velocity A) continuously decreases B) remains zero C) continuously increases D) first decreases and then increases E) remains a non-zero constant 6.) You are trying to cross a river that flows towards the south with a strong current. You start out in your motorboat on the east bank desiring to reach the west bank directly west from your starting point. You should head your motorboat A) in a general northwesterly direction B) directly towards the west C) in a general southwesterly direction D) directly toward the north

Explanation / Answer

1. typically lectures are 1.30 hrs long.

t = (1.30)(3600) s = 4680 sec

Ans(D)

2. t = 6/50 + 6/90 = 0.187 hr

average speed = distance / time = 12 / 0.187 = 64.3 km/h
Ans:(A)

3. slow down means acceleration will be in opposite direction of velocity.

hence acc. is in east direction.
Ans(C)

4. acceleration is always downwards.

Ans(B)

5. (E)

6. (A)

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