CLASS 11 ASSIGNMENT 7 SUMS - MOTION IN A STRAIGHT LINE

 CLASS 11

ASSIGNMENT 7

SUMS - MOTION IN A STRAIGHT LINE


1. A body travels from A to B at 40 m/s and from B to A at 60 m/s.  Find the average speed and average velocity.


2. A car covers the first half of the distance between two places at a speed of 40 km/h and the second half at 60 km/h.  What is the average speed of the car?


3. The displacement of a particle varies with time t as x = 4t² - 15t + 25.  Find the position, velocity and acceleration of the particle at t=0.  When will the velocity of the particle become zero?  Can we call the motion of the particle as one with uniform acceleration?


4. The acceleration of a particle in m/s² is given by  a = 3t²+ 2t + 2, where time t is in second. If the particle starts with a velocity v=2 m/s at t=0, then find the velocity at the end of 2 s.


5.  A jet plane starts from rest with an acceleration of 3 m/s² and makes a run for 35 s before taking off.  What is the minimum length of the runway and what is the velocity of the jet to take off?


6.  A body covers a distance of 20 m in the 7th second and 24 m in the 9th second.  How much shall it cover in 15th second?


7.  A car A moving at 10 m/s on a straight road is ahead of car B moving in the same direction at 6 m/s.  Find the velocity of A relative to B and vice versa.


8.  A man swims in a river with and against water at the rate of 15 km/h and 5 km/h.  Find the man's speed in still water and the speed of the river.


9. A car A is moving with a speed of 60 km/h and car B is moving with a speed of 75 km/h, along parallel straight paths, starting from the same point.  What is the position of car A w.r.t car B after 20 minutes?


10.  A car moving along a straight highway with speed of  126 km/h is brought  to a stop within a distance of 200 m.  What is the retardation of the car (assumed uniform) and how long does it take for the car to stop? 


11. Two trains A and B of length 400 m each are moving on two parallel tracks with a uniform speed of 72 km/h in the same direction, with A ahead of B.  The driver of B decides to overtake A and accelerates by 1 m/s².  If after 50 s, the guard of train B just brushes past the driver of A, what was the original distance between them?


12.  A car is travelling on a straight level road with a speed of 60 km/h.  It is followed by another car B which is moving with a speed of 70 km/h.  When the distance between them is 2.5 km, the car B is given a deceleration of 20 km/h².  After what distance and time will the car B catch up with car A?


13.  Two buses start simultaneously towards each other from towns A and B which are 480 km apart.  The first bus takes 8 hours to travel from A to B while the second bus takes 12 hours to travel from B to A.  Find when and where the buses will meet.


14.  Two trains 120 m and 80 m in length are running in opposite directions with velocities 42 km/h and 30 km/h.  In what time they will completely cross each other?



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