Rest and Motion: Kinematics Physics - Rest and Motion: Kinematics

In a projectile motion the velocity:

1. Is always perpendicular to the acceleration.
2. Is never perpendicular to the acceleration.
3. Is perpendicular to the acceleration for one instant only.
4. Is perpendicular to the acceleration for two instants.

Two bullets are fired simultaneously, horizontally and with different speeds from the same place. Which bullet will hit the ground first?

1. The faster one.
2. The slower one.
3. Both will reach simultaneously.
4. Depends on the masses.

A particle starts from a point A and travels along the solid curve shown in figure. Find approximately the position B of the particle such that the average velocity between the positions A and B has the same direction as the instantaneous velocity at B.

A ball is thrown vertically upward with a speed of 20m/s. Draw a graph showing the velocity of the ball as a function of time as it goes up and then comes back.

When a person leaves his home for sightseeing by his car, the meter reads 12352km. When he returns home after two hours the reading is 12416km.

1. What is the average speed of the car during this period?
2. What is the average velocity?

A bullet travelling with a velocity of 16m/s penetrates a tree trunk and comes to rest in 0.4m. Find the time taken during the retardation.

A food packet is dropped from a plane going at an altitude of 100m. What is the path of the packet as seen from the plane? What is the path as seen from the ground? If someone asks "what is the actual path", what will you answer?

Rain is falling vertically. A man running on the road keeps his umbrella tilted but a man standing on the street keeps his umbrella vertical to protect himself from the rain. But both of them keep their umbrella vertical to avoid the vertical sun-rays. Explain.

A man has to go 50m due north, 40m due east and 20m due south to reach a field.

1. What distance he has to walk to reach the field?
2. What is his displacement from his house to the field?

A swimmer wishes to cross a 500m wide river flowing at 5km/h. His speed with respect to water is 3km/h.

1. If he heads in a direction making an angle 0 with the flow, find the time he takes to cross the river.
2. Find the shortest possible time to cross the river.

A river 400m wide is flowing at a rate of 2.0m/s. A boat is sailing at a velocity of 10m/s with respect to the water, in a direction perpendicular to the river.

1. Find the time taken by the boat to reach the opposite bank.
2. How far from the point directly opposite to the starting point does the boat reach the opposite bank?

An elevator is descending with uniform acceleration. To measure the acceleration, a person in the elevator drops a coin at the moment the elevator starts. The coin is 6ft above the floor of the elevator at the time it is dropped. The person observes that the coin strikes the floor in 1 second. Calculate from these data the acceleration of the elevator.

An aeroplane has to go from a point A to another point B, 500km away due 30° east of north. A wind is blowing due north at a speed of 20m/s. The air-speed of the
plane is 150m/s.

1. Find the direction in which the pilot should head the plane to reach the point B.
2. Find the time taken by the plane to go from A to B.

The benches of a gallery in a cricket stadium are 1m wide and 1m high. A batsman strikes the ball at a level one metre above the ground and hits a mammoth sixer. The ball starts at 35m/s at an angle of 53° with the horizontal. The benches are perpendicular to the plane of motion and the first bench is 110m from the batsman. On which bench will the ball hit?