Question

1) a car is moving due to east covers 1 km in 100 sec. find its speed and velocity.

2) a car is moving with 20m/s is brought to rest by applying brakes in 5 sec. calculate retardation.

3) a body moves from rest with uniform acceleration and travels 270m in 3 sec. find the velocity of the body at 10 sec from the start.

Answer 1

Hi..
Hope this helps u!!

Answer 2

1)
Distance covered:1km=1000m
Time taken:100 seconds
Displacement=Distance(Because the object is moving in a straight path via east)
Speed= Distance÷Time
= 1000÷100
= 10 metres per second
Displacement= Displacement÷time
= 1000÷100
= 10 metres per second
2)
Initial Velocity= 20 m/s
Final velocity= 0m/s
Time taken= 5 seconds
Retardation= (Final velocity-Intial velocity) ÷ time taken
=(0-20)÷5
=-20÷5
=-4m/s^2
3)
Initial Velocity(u)= 0m/s
Distance covered in 3 seconds= 270m
Given that object accelerates uniformly we can conclude that velocity at 3 seconds is 3x.Also distance covered at 3 seconds is 270m.
3x=270
x=90m/s this is the velocity of car at the first second
Acceleration= (final velocity - Initial velocity)÷ time
=(90-0)÷1
=90m/s^2
As acceleration= velocity ÷ time
velocity= acceleration × time
Therefore velocity at ten seconds =90×10
=900m/s