Join 60,000+ competitive exam aspirants
A car covers 120 km in 2 hours. What is its speed in m/s?
16.67 m/s
20 m/s
33.33 m/s
60 m/s
16.67 m/s
Speed is defined as the total distance covered divided by the total time taken. To convert speed from km/h to m/s, we must multiply the value by 185тАЛ because 1┬аkm=1000┬аm and 1┬аhour=3600┬аseconds.
Speed is defined as the total distance covered divided by the total time taken. To convert speed from km/h to m/s, we must multiply the value by 185тАЛ because 1┬аkm=1000┬аm and 1┬аhour=3600┬аseconds.
Think of converting km/h to m/s like changing currency: just as you exchange larger units (Rupees) for smaller units (paise) to count them differently, you break down long distance hours into smaller, precise second-by-second steps.
Remember 'Big to Small, Multiply by Small (5/18); Small to Big, Multiply by Big (18/5)'.
v=tdтАЛ тАФ formula for speed where v is speed, d is distance, and t is time
1┬аkm/h=3600┬аs1000┬аmтАЛ=185тАЛ┬аm/s тАФ unit conversion factor
The principle relies on dimensional analysis and unit conversion factors. By substituting 1000┬аm for 1┬аkm and 3600┬аs for 1┬аh, the conversion factor simplifies to 36001000тАЛ, which reduces to 185тАЛ. Applying this factor maintains the physical equivalence of the speed magnitude across different SI and non-SI units.
Speed is a scalar quantity while velocity is a vector quantity.
The SI unit for speed is meters per second (m/s).
Conversion from km/h to m/s always requires multiplication by 185тАЛ.
Using SI units (m/s) ensures consistency in physics equations like F=ma or KE=21тАЛmv2.
Calculating kinematics for vehicle performance.
Solving projectile motion problems in competitive physics.
Initial speed calculation: 2┬аh120┬аkmтАЛ=60┬аkm/h.
Conversion: 60├Ч185тАЛ=18300тАЛ=16.67┬аm/s.
Option B (20 m/s) is incorrect as it results from dividing by 3, neglecting the unit conversion factor.
A is correct тАФ The speed calculation yields 60┬аkm/h, which converts exactly to 16.67┬аm/s using the conversion factor 185тАЛ.
Always verify if the question asks for the final value in m/s or km/h before final marking, as unit mismatch is the most common cause of error in physics sections.