Question 12 (0.5 points) A 10 N force has an angle of 0 degree with x axis and a

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Question 12 (0.5 points) A 10 N force has an angle of 0 degree with x axis and another force 6 N has an angle of 60 degree with x axis. If you want to add these vectors, what is the total x Your Answer: Question 13 (0.5 points) A stone is thrown vertically upward with velocity 38 m/s. Find the time when the velocity will be 75% of the initial velocity? Your Answer: Save Question 14 (1 point) In the first part of your trip, you drive 65 milles at an average speed of 33 miles/hour. In the second part of your trip, you drive 5 hours at an average speed of 48 mileshour. What is average speed during your whole trip? Your Answer Question 15 (0.5 points) A box slides down an incline with uniform acceleration. It starts from rest and attains a speed of 34.6 m/s in 5.5 sec. What distance the box will move in 26 sec? Your Answer Question 16 (1 point) You traveled 40 minutes at 12 km/h speed and then you speed up to 57 km/h and maintained this speed for certain time. If the total trip was 120 km, how long did you travel at higher speed? Write your answer in minutes. Your Answer

Explanation / Answer

12) Total x-component = sum of the x components of both forces
   = 10 cos 0 + 6 cos 60 = 13 N

13) v= u + at
u = 38 m/s v = 0.75u, a = -g = -9.8 (-ve as it is downward and upward velocity is taken as +ve)
   t = (v - u)/ a = 2.9 sec

14) Time of first part of trip, t1 = 65/33 Hr
Distance travelled in second part of trip = 5*48 = 240 miles
   Average speed = total ditance / total time = (65 + 240) /( 65/33 + 5) = 43.76 miles / Hr

15) Acceleration of box = (v-u)/t = 34.6 / 5.5
   S = ut + 1/2 at2
u= 0, so s = 1/2 a t2 = 1/2 (34.6/5.5) 262 = 2126.3 m

16) Distance covered at constant speed = 12 * 40/60 = 8 km
Dis tance covered at 57 km/h = 120 - 8 = 112 km
Time at higher speed = 112/57 = 1.96 Hr

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