Mechanics | Relativity Answers

a box slides down at constant velocity along an inclined plane which makes angle x with the horizon. if the box is now given an initial velocity v in the upward direction along the plane, what would be the displacement of the box

18 a boy throws a ball vertically upward with a speed of 15.0m/s. what is its speed just before the boy catches it again?

11.5 m/s downward

225.0 m/s downward

15.0 m/s downward

250 m/s downward

18 a boy throws a ball vertically upward with a speed of 15.0m/s. what is its speed just before the boy catches it again?

11.5 m/s downward

225.0 m/s downward

15.0 m/s downward

250 m/s downward



19 a ball is thrown vertically upward with a speed

v

from a point

h

metres above the ground. which of the following correctly expresses the time taken to for the ball to strike the ground?

vg(1+1+2hgv2−−−−−−−√)

vg(1−1+2hgv3−−−−−−−√)

vg(1+1−2hgv2−−−−−−−√)

vg(1+1−2hgv3−−−−−−−√)



20 a body moves along the x-axis according to the law

x=2t3+5t2+5

, where

x

is in metres. find the acceleration at

t=3s

34m/s2

46m/s2

44m/s2

36m/s2

17 a particle moves along the x-axis in such a way that its position at any instant is given by

x−5t2+1

, where

x

is in metres and

t

is in seconds. calculate the instantaneous velocity at 2s.

20ms−1

30ms−1

50ms−1

25ms−1

15 if two vectors are represented in magnitude and direction by adjacent sides of a parallelogram the resultant is represented in magnitude and direction by the __________ drawn from the origin of the vectors

vertices

diagonal

two sides

remaining side



16 a particle moves along the x-axis in such a way that its position at any instant is given by

x−5t2+1

, where

x

is in metres and

t

is in seconds. calculate its average velocity in the time interval between 2s and 3s.

25ms−1

30ms−1

50ms−1

15ms−1

12 a bird flies parralell to a railway track at a speed of 60 km/h. what is the speed of the bird as observed by a passenger in a coach of a train moving on the track in the same direction as the bird at a speed of 160km/h?

220 km/h

240 km/h

100 km/h

120 km/h



13 a driver does a round trip to ibadan from lagos, returning to his take-off point in five hours. the distance of ibadan from lagos is 130 km. what is his average velocity?

52 km/h

26 km/h

0 km/h

104 km/h



14 a booat can travel at a speed of 12 km/h on still water of a river. when the river is flowing at a speed of 3 km/h the boat can also travel at a speed of 3 km/h relative to the water in the river. a boatman using this boat aims to cross the river from point a on the river bank to point b directly opposite to point a on the other bank of the river. how should he aim the boat to achieve this goal?

75.5 degrees upstream

14.5 degrees downstream

75.5 degrees downstream

14.5 degrees upstream

10 given two vectors

a⃗ =4i^−3j^+2k^

,

b⃗ =i^+2j^−k^

, calculate

a⃗ ×b⃗

2^i−6j^−5k^

−i^+6j^+5k^

−i^−6j^+5k^

−2^i−6j^+5k^

11 given the vectors

a⃗ =i^−2j^+3k^

,

b⃗ =2i^+j^−k^

,

c⃗ =3i^−2j^+3k^

calculate

a⃗ ⋅(b⃗ ×c⃗ )

11

-22

-11

22

9 given two vectors

a⃗ =4i^−3j^+2k^

,

b⃗ =i^+2j^−k^

, calculate

a⃗ ⋅b⃗

2

-4

-2

4

vector

a⃗

of length 8 m lies at an angle of

60o

above the x-axis in the first quadrant. vector

b⃗

of length 5 m lies

53o

below the x-axis in the fourth quadrant. determine the magnitude of

a⃗ −b⃗

9.94 m

7.60 m

10.96 m

20.21 m

a synchronous satellite circles the earth eastward above equator once every 24h and stays over the same spot on the earth because the earth is rotating at the same rate. what is the velocity of the synchronous satellite?

9800 m/s

4300 m/s

3100 m/s

2400 m/s