Question

A car of mass 1000kg and travelling with velocity 30 ms-1 stops at a distance of

50m decelerating uniformly. Find

(a) The magnitude of the force exerted on it by the brakes.

(b) The work done by the brakes.​

Answer 1

Answer:

b

Explanation:

the work done by the brakes

Answer 2

Given :-

• Mass of the car = 1000 Kg

• Initial velocity of car = 30 m/s

• Final velocity of car = 0 m/s

• Displacement of car = 50 m

To Find :-

• The magnitude of the force exerted on it by the brakes

• The work done by the brakes

Solution :-

First we have to find acceleration of the car

$\longrightarrow \:\underline{\boxed{ \sf {v}^{2} - {u}^{2} = 2as}} \\ \\ \longrightarrow \: \sf {(0)}^{2} - {(30)}^{2} = 2 \times a \times 50 \\ \\ \longrightarrow \: \sf- 900 = 100a \\ \\\longrightarrow \: \sf a = - \frac{900}{100} \\ \\\longrightarrow \: \underline{\boxed{\sf a = 9 \: {ms}^{ - 2}}}$

Now we can find force exerted by brakes

$\longrightarrow \: \underline{\boxed{\sf F = ma }}\\ \\\longrightarrow \: \sf F = 1000 \times ( - 9) \\ \\\longrightarrow \:\underline{\boxed{ \sf F= - 9000 \: N}}$

- ve sign shows that force is in opposite direction of the car

Now , Work done by the car is

$\longrightarrow \: \underline{\boxed{\sf W= F \times d }}\\ \\\longrightarrow \: \sf W = - 9000 \times 50 \\ \\\longrightarrow \: \underline{\boxed{\sf W = - 45000 \: J}}$