1. A bus was initially travelling with a velocity of 50 km/s east. Later it was

Question

1. A bus was initially travelling with a velocity of 50 km/s east. Later it was observed traveling with a velocity of 100 km/h north. What was the change in velocity of the bus?

2. An object experiences an average acceleration of 4 m/s^2 west for a time of 2 s. Find the object's final velocity (magnitude and direction) given the following initial velocity. (a) 3 m/s west. (b) 6 m/s east.

3. An object experiences an average acceleration of 3 m/s^2 east for a time of 2 s. Find the object's initial velocity (magnitude and direction) given the following final velocities. (a) 8 m/s east. (b) 4 m/s west.

4. A 70-kg stunt pilot pulls out of a dive while flying at 50 m/s. If he flies a circular path with a radius of 200 m, what force does his seat exert on him at the bottom of the path?

5. A ball is thrown horizontally at a speed of 20 m/s over level ground. (a) If it starts out at a height of 19.6 m, how long does it take for the ball to reach the ground? (b) How far will it move horizontally in this time?

6. A ball is launched horizontally at a speed of 40 m/s. With what speed will it hit the gorund if it falls for 3 s?

7. A football is thrown with a vertical speed of 9.8m/s and a horizontal speed of 15 m/s. How far down field should the wide reciever be to catch this pass?

Please show work and explain.

Explanation / Answer

1. change in velocity =   sqrt ( 100 ^ 2   + 50^2)    =   111.81 m/s

2. a)   velocity = 3+ 4*2 = 11 m/s

    b) velocity   = -6 + 4* 2   = 2m/s

3. a) v      =   8 + 3*2 = 14 m/s

b) v   = - 4   + 3*2 = 2m/s

4 . SEAT BELT FORCE provides him the centripetal force = mv^2/r    =   70 * 50^2 / 200   = 875 N

5) a)   time taken = sqrt ( 2 * height /g) = sqrt ( 2* 19.6 /9.8) = 2s

     b) distance = horizontal velocity * time = 20 *2   = 40 m

6) vertical velocity = 9.8 * 3 = 29.4 m/s

horizontal = 40 m/s

net   = sqrt ( 40 ^2    + 29.4 ^ 2 )   = 49.64 m/s

.7) range of projectile = horizontal velocity * 2* vertical velocity /g = 30 m

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