Mechanics | Relativity Answers

if a body is displaced through height h, workdone will be -mgh.but when we see in interconversion of energy it take P.E=mgh

coefficient of static friction is .36
coefficient of kinetic friction is .30
weight of box 400N

how much force is needed to keep the box moving

Two cars X and Y are travelled in the same direction with velocity V1 and V2 (V1> V2).when the car X is at a distdistance S behind the car Y,the car X starts deaccelaration with A.to avoid the collision......

A stone is dropped from a balloon moving upwards at 20m/s at a height at 105m.distance travelled by the stone, just before reaching the ground.....
A) 125 . B) 145m. C) 130m. D) 120m

A 2.5 kg block is kept on a 3.2 kg block resting on the floor of an elevator. If the elevator is moving up at 1.3 m/s2, calculate the force exerted by the 2.5 kg block on the 3.2 kg block.

A particle P is moving in a circle of radus r with uniform speed v. C is the centre of the circle and AB is diameter. The angular velocity of P about A and C is in the ratio
1. 4:1
2. 2:1
3. 1:2
4. 1:1

on a foggy day, two drivers spot in front of each other when 80 metre apart. They were travelling at 70kmph and 60kmph. Both apply brakes simultaneously which retard the cars at the rate 5 m/s^2. Which of the following statements is correct?
1. The collision will be averted
2. The collision will take place
3. They will cross each othe
4. They will just collide

a boat takes two hours to travel 8km down and 8 km up the river when the water is till. How much time will the boat take to make the same trip when the river starts flowing at 4kmph?
1. 2 hours
2. 2 hour 40 minutes
3. 3 hours
4. 3 hour 40 minutes

A lorry travels along a rough road at 30km for 30mins. If the lorry joins a tarred road and moves at 550km for 1hour.Calculate the average speed of the lorry in m/s

Water drops are coming down at regular time interval from a tap 1.8m high such that when first drop is about to hit the ground the fourth drop is starting off.the position of the third drop from the ground is....
A) 1m. B).6m. C).8m. D) 1.6m