Motion in a Plane · Question 42

If a vector 2 i + 3 j + 8 k is perpendicular to the vector 4 j - 4 i + k, then the value of is

1. 1/2
2. -1/2
3. 1
4. -1.

If | A B| = 3 A B then the value of | A + B| is

1. (A2 + B2 + AB)1/2
2. (A2 + B2 + AB 3 )1/2
3. A + B
4. (A2 + B2 + 3AB)1/2

The vector sum of two forces is perpendicular to their vector differences. In that case, the forces

1. are equal to each other
2. are equal to each other in magnitude
3. are not equal to each other in magnitude
4. cannot be predicted.

A particle moves along a circle of radius ( 20 ) m with constant tangential acceleration. If the velocity of the particle is 80 m/s at the end of the second revolution after motion has begun, the tangential acceleration is

1. 40 m/s2
2. 640 m/s2
3. 160 m/s2
4. 40 m/s2

A particle A is dropped from a height and another particle B is projected in horizontal direction with speed of 5 m/sec from the same height then correct statement is

1. particle A will reach at ground first with respect to particle B
2. particle B will reach at ground first with respect to particle A
3. both particles will reach at ground simultaneously
4. both particles will reach at ground with same speed.

If | A + B | = | A | + | B |, then angle between A and B will be

1. 90
2. 120
3. 0
4. 60

Two particles having mass M and m are moving in a circular path having radius R and r. If their time periods are the same, then the ratio of their angular velocities will be

1. rR
2. Rr
3. 1
4. Rr

A particle is projected making an angle of 45 with horizontal having kinetic energy K. The kinetic energy at highest point will be

1. K 2
2. K2
3. 2K
4. K

The width of river is 1 km. The velocity of boat is 5 km/hr. The boat covered the width of river along the shortest path in 15 min. Then the velocity of river stream is

1. 3 km/hr
2. 4 km/hr
3. 29 km/hr
4. 41 km/hr

Two projectiles of same mass and with same velocity are thrown at an angle 60 and 30 with the horizontal, then which will remain same

1. time of flight
2. range of projectile
3. maximum height acquired
4. all of them